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Skin response to histamine dry skin prick test: Influence of duration of the skin prick on clinical parameters and on skin blood flow monitoring
Journal of Dermatological Science, 1 (1990) 435-440 Elsevier
435
DESC 00047
Skin response to histamine dry skin prick test: Influence of duration of the skin prick on clinical parameters and on skin blood flow monitoring D. Van Neste Skin Study Center, Skintet$ace SPRY, Tournai, Belgium (Received 5 January
Key words: Histamine;
1990; accepted
Laser Doppler flowmetry;
1 June 1990)
Skin prick tests; Quantitative
in vivo method
Abstract
This comparative trial (histamine dry skin prick test versus control prick test) evaluates with subjective and objective clinical methods (i.e. itch scores, wheal area, and wheal and flare area) and with laser Doppler flowmetry (multiple sites measured between 5 and 15 min after prick test) the effect of increasing the duration of the skin prick (1,3 and 10 s). As compared with control prick tests, all objective clinical parameters after histamine prick test were significantly different from the control prick tests. There was no interaction between agonist-duration of prick test and clinical parameters. When present, itch was reported only after histamine prick test. Skin blood perfusion values were evaluated with Laser Doppler flowmetry at prick test sites and at 1 cm distance from the prick test site. At control and histamine prick test sites, increased blood flow values were observed and a moderate interaction between agonist-duration of prick test and repeated measurement was noted (one tail P < 0.05); there were indeed lower values 9 min after histamine prick tests whatever the duration of the prick test. At 1 cm distance from histamine prick test sites, all skin perfusion measurements (either 5-8 or 11-14 min) showed increased values over data recorded after control prick test (P < 0.0001). On pooled data recorded at distance from histamine or control prick tests, there was a significant interaction between agonist-duration of prick test and laser Doppler flowmetry (P < 0.0004). Indeed, only moderate changes were recorded at distance from the control prick test, with the exception of the reaction induced by the 10 s control prick duration, where highly significant increases of blood flow were recorded 11-14 min after testing. This reflects activation of the axon reflex mediated vasodilation only after prolonged duration of the control prick. Laser Doppler flowmetry appears to be a reliable and highly sensitive method for objective quantitative measure of skin blood perfusion at sites of and at distance from histamine injection with the dry skin prick test; short duration (i.e. 1 s) is recommended in order to record specific histamine related signals in a repeatable way.
Introduction
The injection of histamine into human skin results in a typical wheal and flare reaction. This reaction pattern develops within minutes in the Correspondence to: D. Van Neste, Skinterface SPRL, 9 rue du Sondart, B 7500 Tournai, Belgium. 0923-181 l/90/$03.50
0 1990 Elsevier Science Publishers
immediate surroundings of the agonist injection [for a review see 11. In recent years, new technologies have been used separately (telethermography [ 21; laser Doppler flowmetry [ 31, or in combination [4], for the evaluation of the skin reaction after intradermal injection of histamine. Changes recorded at sites of histamine injection are influenced by a
B.V. (Biomedical
Division)
436
mixed response: one part is being generated by the microtrauma (prick test), the other by the edematous wheal reaction (histamine specific response). At distance from the prick test axon reflex dependent vasodilation is recorded. This might be responsible for the lack of consistency of results published in the literature because data were recorded at various sites of the agonist induced reaction [ 3-71. While it is difficult to differentiate between control and histamine responses in the center of the wheal [3], easy discrimination with measurements made at 1 cm distances from the injection site has been reported [3-5, 8-l 13. In order to minimize as much as possible non specific factors associated with agonist administration (volume of saline, speed and depth of injection.. .), we used the dry skin prick test, a ready to use disposable material. Using this material in previous experiments, acceptable reproducibility was observed as well at injection sites or at distance from it [4,5,8-10 and personal unpublished data]. The relative importance of the duration of the prick test has not been questioned in great detail. In earlier trials, we used the 1 s duration which had been established in experiments performed with antigen extracts [ 121. Herein, we report the results of a comparative study designed to evaluate the effect of the duration of the injection time i.e. 1,3 and 10 s on the skin response using the histamine and control dry skin prick tests. Material
AB, Sweden) was firmly pressed into the skin and maintained in that position for 1, 3 or 10 s. Prick tests with unloaded needles were performed in the same way and served as a negative control. Skin blood perfusion measurements The measurements were performed with laser Doppler flowmetry (LDF; Periflux PF3, Perimed, Sweden). This instrument displays continuously the intensity of skin perfusion units (PU) on a digital screen. The probe of the LDF was inserted into commercially available probe holders. For the specific purpose of this experiment, the central part of 5 such probeholders was cut out and reassembled in such way as to provide the constant 1 cm distance/orientation between the central and peripheral measurement point [ 41. The central measurement site was carefully overlaid onto the prick test site under visual control through the hole of the central probeholder and when the whole asset was properly oriented it was taped to the skin surface with double sided adhesive (Tesafix, Beiersdorf AG, F.R.G.). Itch scores 10 min after prick tests, the patients were asked to evaluate the intensity of the itch sensation. The scores were as follows: 0: no itch; 1: minimal itch sensation, 2: moderate itch sensation; 3: intense sensation with tendency to develop scratch response in the surroundings of the test site; 4: unbearable itch.
and Methods
Subjects Ten subjects volunteered for this study which was accepted by the committee on ethics on human investigation (IMC, Tournai, Belgium). The site used in this investigation was located on the volar aspect of the forearm (at 5 cm from the volar fold). Skin prick tests Histamine was administered using the dry skin prick test method. The disposable prick needle (PHAZETTM ; generously supplied by Pharmacia
Wheal and wheal and flare area 10 min after prick tests, the wheal and wheal and flare areas were outlined with a skin marker. The borders were drawn on a transparency at the end of the experiment and the area evaluated with automated computer assisted image analysis (W. De Coster; Center for Image Analysis and Quality Control; CEBAN, University of Ghent, Ghent, Belgium). Experimental design After measuring basal blood flow, and 5 min after prick test, probing of the skin vascular
response was started. Measurements were recorded every 5’h s during a 50 s period. The probe was then moved to the next point and readings were started after 10 s stabilization period. A first set of data was recorded as described on preprinted data recording sheets in the following sequence at 1 cm from the injection site: proximal (5’h min), external (gfh min), distal (7’h min) and internal (Sth min). Finally the last measurement started during the gfh minute and was made exactly at the site of injection of histamine. The whole asset was then removed from the test site for outlining the wheal and flare areas. After asking for itch intensity scores, a second set of measurements was recorded between the 1 l’h-14th and during the 15’h min after prick testing respectively at distance from and at skin prick test site. As a control we performed a skin prick test with an unloaded skin prick test and repeated the test with the same durations as described for the histamine prick tests. The clinical scores and measurements were made exactly in the same way as for the histamine loaded needles. Statistical analysis Bar graphs represent the average of the sample for all objective measurements (n = 10). Subjective data are shown individually (e.g. itch). Clinical parameters after prick tests and differential skin perfusion units (6PU = values recorded at time ‘t’ after prick test - values recorded at that site before prick test) were assessed with analysis of variance for repeated measurements (ANOVA) using agonist (histamine vs control), duration of prick test (1, 3 or 10 s) as factors. Changes are considered significant when P < 0.05 (two tailed); when one tail P < 0.05, changes are described as moderate. Results Clinical changes observed after control and histamine prick test As compared with control prick tests, all objective clinical parameters after histamine prick test were significantly different from the control prick
3
10 duration (s)
1200 -
mm sq
~=“-
1
3
IO duration (s)
Fig. 1. Objective clinical parameters as a function of duration of skin prick test. Average of objective clinical parameters (la: wheal area, mm sq; lb: wheal and flare area, mm sq) are shown as a function of duration of skin prick test (histamine: plain columns, control: void columns). There is a clear-cut agonist influence as minimal changes were noted after control prick test (P < 0.0002), but duration of prick test (1, 3 or 10 s) does not modulate this response.
tests (P < 0.0002). Analysis of variance for repeated measurements showed no significant interaction between agonist-duration of prick test and clinical parameters. The objective clinical data are shown in Fig. 1. When present (7/ 10) itch was reported only in case of histamine prick test. This parameter showed much variation between and within individuals (Fig. 2).
438
itch score a 3 1
1 2 1
1
1
0
ILL 1
3
10 duration (s)
2
subject
Fig. 2. Subjective parameter ‘itch’ as a function of duration of histamine dry skin prick tests. As no itch was experienced after control prick tests, individual itch scores recorded at 10 min after histamine prick tests are displayed as columns for 1 s (plain), 3 s (void) and 10 s (hatched). Individuals No. 2, No. 5 and No. 10 experienced no itch. Subjects No. 1, No. 8 and No. 9 showed stable responses whatever the duration of the prick test. Variable responses were recorded in subjects No. 3, No. 4, No. 6 and No. 7.
apu
““7 b
1
Skin blood perfusion units Skin blood perfusion values were evaluated with Laser Doppler flowmetry at prick test sites and at 1 cm distance from the prick test site. At control and histamine prick test sites (Fig. 3a), increased blood flow values were observed and a moderate interaction between agonist-duration of prick test and repeated measurement was noted (one tail P < 0.05); there were indeed lower values 9 min after histamine prick tests whatever the duration of the prick test. At distance from histamine prick test sites (Fig. 3b), all skin perfusion measurements (either 5-8 or 11-14 min) showed increased values over data recorded after control prick test (agonist effect: P < 0.0001). There was also a significant interaction between agonist-duration of prick test and repeated measurement (P < 0.0004). Indeed, only moderate changes were recorded at distance from the control prick test, with the exception of the 10 s control prick test, where significant increases of blood flow were recorded between 11 and 14 min
3
10 duration (s)
Fig. 3. Skin blood perfusion after skin prick tests. Data shown are differential skin perfusion units (6PU) recorded at skin prick test sites (3a) or at 1 cm distances from it (3b). For each prick duration (1,3 or 10 s) two pairs of bars are shown (averages of the group). One pair of bars shows histamine prick test data (HP), the other shows control prick test data (CP). (3a) The histamine (left pair of bars) and control (right pair of bars) responses are shown for two different recording periods (9 min, plain columns or 15 min. hatched columns) according to duration of prick tests (1, 3 and 10 s). There is a moderate interaction between agonist and duration ofprick test (one tail P < 0.05). With 1 s and 10 s histamine prick tests, data recorded at 9 min are lower than those present 15 min after histamine. (3b) The histamine (left pair of bars) and control (right pair of bars) responses are shown for two different recording periods (5-8 min, plain columns or 11-14 min, hatched columns) according to duration of prick tests (1, 3 and 10 s). Pooled data recorded in 4 directions around skin prick tests show constant increases after histamine as compared to control prick test. Besides the agonist effect (P < 0.0002), measurements are also influenced by duration of prick test (P < 0.002). This indicates non specific increases of skin blood perfusion around the 10 s prick test (agonist-duration and measurement interaction, P-c 0.0004).
439
after testing. This reflects activation of the axon reflex mediated vasodilation only after prolonged duration of the control prick. Discussion Increases of skin blood flow occur in the center of the wheal and in the erythematous flare associated with histamine injection in the skin. When 4 different measurement points are explored within the erythematous flare, there is no significant effect of the duration of the histamine prick test; in control prick tests, even though no erythema is visible, significant increases of skin blood perfusion are recorded at 1 cm distances from the 10 s prick test. This indicates that the duration of the prick test is a significant factor to take into consideration when histamine specific effects are to be evaluated and illustrates the higher sensitivity of laser Doppler flowmetry over clinical examination. Therefore, we recommend to use short prick test durations (i.e. 1 s) in order to prevent any interactive effects, in this case of mechanical origin, that could interfere with initiation by the agonist of the axon reflex mediated vascular response. This is of special importance when evaluating agonist-antagonist interactions. It is interesting to note that skin perfusion recorded at the prick test site are lower when measured at 9 min after histamine as compared to 9 min after control prick test. The blood flow increases later on when the wheal fades away. This supports the view that the edematous wheal reduces transiently the blood flow which shows sharp increases associated with the microinjury induced by the skin prick test. Similar moderate changes were indeed noted during earlier experiments using the same material and histamine solutions as well [ 51. These data suggest that early recordings performed at histamine injection sites might be even more appropriate than measures at distance from it for evaluating specifically the histamine induced response, provided that the injection method shows high reproducibility. This concept might also be extended to methods currently in use in human pharmacology during drug discovery of topical agents aimed at modulating type-1 allergy [ 131.
References 1 Foreman JC: histamine, histamine antagonists, and cromones, in: Pharmacology of the skin. I. Pharmacology of skin systems, autocoids in normal and inflamed skin. Edited by MW Greaves, S Shuster. Springer, Berlin, 1989, pp. 289-308. 2 Stiittgen G, Eilers J: Reflex heating of the skin and telethermography. Arch Dermatol Res 272: 301-310, 1982. 3 Serup J, Staberg B: Quantification ofweal reactions with laser Doppler flowmetry. Allergy 40: 233-237, 1985. 4 Van Neste D: Etude comparative de deux mCthodes d’kvaluation non invasives de la rCponse cutanee d I’histamine: ttl&thermographie versus laser Doppler vClocimetrie. Nouv Dermatol 9: 32-35, 1990. 5 Van Neste D, Rihoux JP: Inhibition of the cutaneous response to histamine by Hl-blocking agents. A quantitative evaluation of microvascular changes in the skin after histamine challenge and a comparison of the effects of a single intake of cetirizine and terfenadine. Skin Pharmacology 1: 192-199, 1988. 6 Shall L, Marks R: Non-invasive instrumental techniques to detect terfenadine and temelastine induced suppression of histamine induced weals in man. Br J Clin Pharmac 24: 409-413, 1987. I Maurice PDL, Barr RM, Koro 0, Greaves MW: The effect of prostaglandin D2 on the response of human skin to histamine. J Invest Dermatol 89: 245-248, 1987. 8 Van Neste D, Coussement C, Rihoux JP: Validation d’une nouvelle mtthode d’evaluation de la rkponse cutante & l’histamine et inter&t pour 1’Ctude comparative de substances antihistaminiques. Nouv Dermatol 8: 5 l-57, 1989. 9 Rihoux, JP, Van Neste D: Quantitative time course study of the skin response to histamine and the effect of Hl blockers. A three weeks crossover double-blind comparative trial ofcetirizine and terfenadine. Dermatologica 179: 129-134, 1989. 10 Van Neste D, Ghys L, Antoine JL, Rihoux JP: Pharmacological modulation by cetirizine and atropine of the histamine and methacholine induced wheals and flares in human skin. Skin Pharmacology 2: 93-102, 1989. 11 Bircher A.J, Maibach H.1: The assessment of the cutaneous microcirculation by laser Dopper and photoplethysmographic techniques: an update in: Models Dermatol. Edited by HI Maibach, NJ Lowe. Karger, Basel, 1989, ~014, pp 209-232. 12 Dreborg S: The skin prick test: methodological studies and clinical applications. Linkiiping University Dissertation N” 239, 1987, pp l-148. 13 Gibson JR: Topically applied drugs in type I allergic reactions, in: Models Dermatol. Edited by HI Maibach, NJ Lowe. Karger, Base], 1989, ~014, pp 240-248.
435
DESC 00047
Skin response to histamine dry skin prick test: Influence of duration of the skin prick on clinical parameters and on skin blood flow monitoring D. Van Neste Skin Study Center, Skintet$ace SPRY, Tournai, Belgium (Received 5 January
Key words: Histamine;
1990; accepted
Laser Doppler flowmetry;
1 June 1990)
Skin prick tests; Quantitative
in vivo method
Abstract
This comparative trial (histamine dry skin prick test versus control prick test) evaluates with subjective and objective clinical methods (i.e. itch scores, wheal area, and wheal and flare area) and with laser Doppler flowmetry (multiple sites measured between 5 and 15 min after prick test) the effect of increasing the duration of the skin prick (1,3 and 10 s). As compared with control prick tests, all objective clinical parameters after histamine prick test were significantly different from the control prick tests. There was no interaction between agonist-duration of prick test and clinical parameters. When present, itch was reported only after histamine prick test. Skin blood perfusion values were evaluated with Laser Doppler flowmetry at prick test sites and at 1 cm distance from the prick test site. At control and histamine prick test sites, increased blood flow values were observed and a moderate interaction between agonist-duration of prick test and repeated measurement was noted (one tail P < 0.05); there were indeed lower values 9 min after histamine prick tests whatever the duration of the prick test. At 1 cm distance from histamine prick test sites, all skin perfusion measurements (either 5-8 or 11-14 min) showed increased values over data recorded after control prick test (P < 0.0001). On pooled data recorded at distance from histamine or control prick tests, there was a significant interaction between agonist-duration of prick test and laser Doppler flowmetry (P < 0.0004). Indeed, only moderate changes were recorded at distance from the control prick test, with the exception of the reaction induced by the 10 s control prick duration, where highly significant increases of blood flow were recorded 11-14 min after testing. This reflects activation of the axon reflex mediated vasodilation only after prolonged duration of the control prick. Laser Doppler flowmetry appears to be a reliable and highly sensitive method for objective quantitative measure of skin blood perfusion at sites of and at distance from histamine injection with the dry skin prick test; short duration (i.e. 1 s) is recommended in order to record specific histamine related signals in a repeatable way.
Introduction
The injection of histamine into human skin results in a typical wheal and flare reaction. This reaction pattern develops within minutes in the Correspondence to: D. Van Neste, Skinterface SPRL, 9 rue du Sondart, B 7500 Tournai, Belgium. 0923-181 l/90/$03.50
0 1990 Elsevier Science Publishers
immediate surroundings of the agonist injection [for a review see 11. In recent years, new technologies have been used separately (telethermography [ 21; laser Doppler flowmetry [ 31, or in combination [4], for the evaluation of the skin reaction after intradermal injection of histamine. Changes recorded at sites of histamine injection are influenced by a
B.V. (Biomedical
Division)
436
mixed response: one part is being generated by the microtrauma (prick test), the other by the edematous wheal reaction (histamine specific response). At distance from the prick test axon reflex dependent vasodilation is recorded. This might be responsible for the lack of consistency of results published in the literature because data were recorded at various sites of the agonist induced reaction [ 3-71. While it is difficult to differentiate between control and histamine responses in the center of the wheal [3], easy discrimination with measurements made at 1 cm distances from the injection site has been reported [3-5, 8-l 13. In order to minimize as much as possible non specific factors associated with agonist administration (volume of saline, speed and depth of injection.. .), we used the dry skin prick test, a ready to use disposable material. Using this material in previous experiments, acceptable reproducibility was observed as well at injection sites or at distance from it [4,5,8-10 and personal unpublished data]. The relative importance of the duration of the prick test has not been questioned in great detail. In earlier trials, we used the 1 s duration which had been established in experiments performed with antigen extracts [ 121. Herein, we report the results of a comparative study designed to evaluate the effect of the duration of the injection time i.e. 1,3 and 10 s on the skin response using the histamine and control dry skin prick tests. Material
AB, Sweden) was firmly pressed into the skin and maintained in that position for 1, 3 or 10 s. Prick tests with unloaded needles were performed in the same way and served as a negative control. Skin blood perfusion measurements The measurements were performed with laser Doppler flowmetry (LDF; Periflux PF3, Perimed, Sweden). This instrument displays continuously the intensity of skin perfusion units (PU) on a digital screen. The probe of the LDF was inserted into commercially available probe holders. For the specific purpose of this experiment, the central part of 5 such probeholders was cut out and reassembled in such way as to provide the constant 1 cm distance/orientation between the central and peripheral measurement point [ 41. The central measurement site was carefully overlaid onto the prick test site under visual control through the hole of the central probeholder and when the whole asset was properly oriented it was taped to the skin surface with double sided adhesive (Tesafix, Beiersdorf AG, F.R.G.). Itch scores 10 min after prick tests, the patients were asked to evaluate the intensity of the itch sensation. The scores were as follows: 0: no itch; 1: minimal itch sensation, 2: moderate itch sensation; 3: intense sensation with tendency to develop scratch response in the surroundings of the test site; 4: unbearable itch.
and Methods
Subjects Ten subjects volunteered for this study which was accepted by the committee on ethics on human investigation (IMC, Tournai, Belgium). The site used in this investigation was located on the volar aspect of the forearm (at 5 cm from the volar fold). Skin prick tests Histamine was administered using the dry skin prick test method. The disposable prick needle (PHAZETTM ; generously supplied by Pharmacia
Wheal and wheal and flare area 10 min after prick tests, the wheal and wheal and flare areas were outlined with a skin marker. The borders were drawn on a transparency at the end of the experiment and the area evaluated with automated computer assisted image analysis (W. De Coster; Center for Image Analysis and Quality Control; CEBAN, University of Ghent, Ghent, Belgium). Experimental design After measuring basal blood flow, and 5 min after prick test, probing of the skin vascular
response was started. Measurements were recorded every 5’h s during a 50 s period. The probe was then moved to the next point and readings were started after 10 s stabilization period. A first set of data was recorded as described on preprinted data recording sheets in the following sequence at 1 cm from the injection site: proximal (5’h min), external (gfh min), distal (7’h min) and internal (Sth min). Finally the last measurement started during the gfh minute and was made exactly at the site of injection of histamine. The whole asset was then removed from the test site for outlining the wheal and flare areas. After asking for itch intensity scores, a second set of measurements was recorded between the 1 l’h-14th and during the 15’h min after prick testing respectively at distance from and at skin prick test site. As a control we performed a skin prick test with an unloaded skin prick test and repeated the test with the same durations as described for the histamine prick tests. The clinical scores and measurements were made exactly in the same way as for the histamine loaded needles. Statistical analysis Bar graphs represent the average of the sample for all objective measurements (n = 10). Subjective data are shown individually (e.g. itch). Clinical parameters after prick tests and differential skin perfusion units (6PU = values recorded at time ‘t’ after prick test - values recorded at that site before prick test) were assessed with analysis of variance for repeated measurements (ANOVA) using agonist (histamine vs control), duration of prick test (1, 3 or 10 s) as factors. Changes are considered significant when P < 0.05 (two tailed); when one tail P < 0.05, changes are described as moderate. Results Clinical changes observed after control and histamine prick test As compared with control prick tests, all objective clinical parameters after histamine prick test were significantly different from the control prick
3
10 duration (s)
1200 -
mm sq
~=“-
1
3
IO duration (s)
Fig. 1. Objective clinical parameters as a function of duration of skin prick test. Average of objective clinical parameters (la: wheal area, mm sq; lb: wheal and flare area, mm sq) are shown as a function of duration of skin prick test (histamine: plain columns, control: void columns). There is a clear-cut agonist influence as minimal changes were noted after control prick test (P < 0.0002), but duration of prick test (1, 3 or 10 s) does not modulate this response.
tests (P < 0.0002). Analysis of variance for repeated measurements showed no significant interaction between agonist-duration of prick test and clinical parameters. The objective clinical data are shown in Fig. 1. When present (7/ 10) itch was reported only in case of histamine prick test. This parameter showed much variation between and within individuals (Fig. 2).
438
itch score a 3 1
1 2 1
1
1
0
ILL 1
3
10 duration (s)
2
subject
Fig. 2. Subjective parameter ‘itch’ as a function of duration of histamine dry skin prick tests. As no itch was experienced after control prick tests, individual itch scores recorded at 10 min after histamine prick tests are displayed as columns for 1 s (plain), 3 s (void) and 10 s (hatched). Individuals No. 2, No. 5 and No. 10 experienced no itch. Subjects No. 1, No. 8 and No. 9 showed stable responses whatever the duration of the prick test. Variable responses were recorded in subjects No. 3, No. 4, No. 6 and No. 7.
apu
““7 b
1
Skin blood perfusion units Skin blood perfusion values were evaluated with Laser Doppler flowmetry at prick test sites and at 1 cm distance from the prick test site. At control and histamine prick test sites (Fig. 3a), increased blood flow values were observed and a moderate interaction between agonist-duration of prick test and repeated measurement was noted (one tail P < 0.05); there were indeed lower values 9 min after histamine prick tests whatever the duration of the prick test. At distance from histamine prick test sites (Fig. 3b), all skin perfusion measurements (either 5-8 or 11-14 min) showed increased values over data recorded after control prick test (agonist effect: P < 0.0001). There was also a significant interaction between agonist-duration of prick test and repeated measurement (P < 0.0004). Indeed, only moderate changes were recorded at distance from the control prick test, with the exception of the 10 s control prick test, where significant increases of blood flow were recorded between 11 and 14 min
3
10 duration (s)
Fig. 3. Skin blood perfusion after skin prick tests. Data shown are differential skin perfusion units (6PU) recorded at skin prick test sites (3a) or at 1 cm distances from it (3b). For each prick duration (1,3 or 10 s) two pairs of bars are shown (averages of the group). One pair of bars shows histamine prick test data (HP), the other shows control prick test data (CP). (3a) The histamine (left pair of bars) and control (right pair of bars) responses are shown for two different recording periods (9 min, plain columns or 15 min. hatched columns) according to duration of prick tests (1, 3 and 10 s). There is a moderate interaction between agonist and duration ofprick test (one tail P < 0.05). With 1 s and 10 s histamine prick tests, data recorded at 9 min are lower than those present 15 min after histamine. (3b) The histamine (left pair of bars) and control (right pair of bars) responses are shown for two different recording periods (5-8 min, plain columns or 11-14 min, hatched columns) according to duration of prick tests (1, 3 and 10 s). Pooled data recorded in 4 directions around skin prick tests show constant increases after histamine as compared to control prick test. Besides the agonist effect (P < 0.0002), measurements are also influenced by duration of prick test (P < 0.002). This indicates non specific increases of skin blood perfusion around the 10 s prick test (agonist-duration and measurement interaction, P-c 0.0004).
439
after testing. This reflects activation of the axon reflex mediated vasodilation only after prolonged duration of the control prick. Discussion Increases of skin blood flow occur in the center of the wheal and in the erythematous flare associated with histamine injection in the skin. When 4 different measurement points are explored within the erythematous flare, there is no significant effect of the duration of the histamine prick test; in control prick tests, even though no erythema is visible, significant increases of skin blood perfusion are recorded at 1 cm distances from the 10 s prick test. This indicates that the duration of the prick test is a significant factor to take into consideration when histamine specific effects are to be evaluated and illustrates the higher sensitivity of laser Doppler flowmetry over clinical examination. Therefore, we recommend to use short prick test durations (i.e. 1 s) in order to prevent any interactive effects, in this case of mechanical origin, that could interfere with initiation by the agonist of the axon reflex mediated vascular response. This is of special importance when evaluating agonist-antagonist interactions. It is interesting to note that skin perfusion recorded at the prick test site are lower when measured at 9 min after histamine as compared to 9 min after control prick test. The blood flow increases later on when the wheal fades away. This supports the view that the edematous wheal reduces transiently the blood flow which shows sharp increases associated with the microinjury induced by the skin prick test. Similar moderate changes were indeed noted during earlier experiments using the same material and histamine solutions as well [ 51. These data suggest that early recordings performed at histamine injection sites might be even more appropriate than measures at distance from it for evaluating specifically the histamine induced response, provided that the injection method shows high reproducibility. This concept might also be extended to methods currently in use in human pharmacology during drug discovery of topical agents aimed at modulating type-1 allergy [ 131.
References 1 Foreman JC: histamine, histamine antagonists, and cromones, in: Pharmacology of the skin. I. Pharmacology of skin systems, autocoids in normal and inflamed skin. Edited by MW Greaves, S Shuster. Springer, Berlin, 1989, pp. 289-308. 2 Stiittgen G, Eilers J: Reflex heating of the skin and telethermography. Arch Dermatol Res 272: 301-310, 1982. 3 Serup J, Staberg B: Quantification ofweal reactions with laser Doppler flowmetry. Allergy 40: 233-237, 1985. 4 Van Neste D: Etude comparative de deux mCthodes d’kvaluation non invasives de la rCponse cutanee d I’histamine: ttl&thermographie versus laser Doppler vClocimetrie. Nouv Dermatol 9: 32-35, 1990. 5 Van Neste D, Rihoux JP: Inhibition of the cutaneous response to histamine by Hl-blocking agents. A quantitative evaluation of microvascular changes in the skin after histamine challenge and a comparison of the effects of a single intake of cetirizine and terfenadine. Skin Pharmacology 1: 192-199, 1988. 6 Shall L, Marks R: Non-invasive instrumental techniques to detect terfenadine and temelastine induced suppression of histamine induced weals in man. Br J Clin Pharmac 24: 409-413, 1987. I Maurice PDL, Barr RM, Koro 0, Greaves MW: The effect of prostaglandin D2 on the response of human skin to histamine. J Invest Dermatol 89: 245-248, 1987. 8 Van Neste D, Coussement C, Rihoux JP: Validation d’une nouvelle mtthode d’evaluation de la rkponse cutante & l’histamine et inter&t pour 1’Ctude comparative de substances antihistaminiques. Nouv Dermatol 8: 5 l-57, 1989. 9 Rihoux, JP, Van Neste D: Quantitative time course study of the skin response to histamine and the effect of Hl blockers. A three weeks crossover double-blind comparative trial ofcetirizine and terfenadine. Dermatologica 179: 129-134, 1989. 10 Van Neste D, Ghys L, Antoine JL, Rihoux JP: Pharmacological modulation by cetirizine and atropine of the histamine and methacholine induced wheals and flares in human skin. Skin Pharmacology 2: 93-102, 1989. 11 Bircher A.J, Maibach H.1: The assessment of the cutaneous microcirculation by laser Dopper and photoplethysmographic techniques: an update in: Models Dermatol. Edited by HI Maibach, NJ Lowe. Karger, Basel, 1989, ~014, pp 209-232. 12 Dreborg S: The skin prick test: methodological studies and clinical applications. Linkiiping University Dissertation N” 239, 1987, pp l-148. 13 Gibson JR: Topically applied drugs in type I allergic reactions, in: Models Dermatol. Edited by HI Maibach, NJ Lowe. Karger, Base], 1989, ~014, pp 240-248.