BALDNESS AND MINOXIDIL

910 of exposure, further emphasising the hazard of recycling textiles.3,4Employers should arrange educational programmes and should monitor security measures to prevent accidental or deliberate removal of asbestos-contaminated materials from the worksite.

exposed. However, I would be cautious about asking for the removal of a potentially useful microbicide from all leave-on products until the discrepancies in prevalence of sensitivity to kathon CG and the significance of positive skin test responses are more fully understood.

Clinical Epidemiology Branch, National Cancer Institute; and Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA

Department of Dermatology, Mayo Clinic, Rochester, Minnesota 55905, USA

one source

asbestos-contaminated

FREDERICK P. LI MARGARET G. DREYFUS KAREN H. ANTMAN

1. Li FP, Lokich J, Lapey J, Neptune WB, Wilkins EW. Familial mesothelioma after intense asbestos exposure at home. JAMA 1978; 240: 467. 2. Anderson HA, Lilis R, Daum SM, Fischbein AS, Selikoff IJ. Household-contact asbestos neoplastic risk. Ann NY Acad Sci 1976, 271: 311-32 3. Vianna NJ, Polan AK. Non-occupational exposure to asbestos and malignant mesothelioma in females. Lancet 1978; i- 1061-63. 4. Quinn MM, Kridbel D, Buiatti E, et al. An asbestos hazard in the reprocessed textile industry. Am J Ind Med 1987; 11: 255-66.

ISOTHIAZOLINONE SENSITIVITY

SiR,—The ideal preservative-non-irritating, non-sensitising, cosmetically acceptable, and with broad-spectrum microbicidal activity-has not yet been found. Dr de Groot and Dr Herxheimer (Feb 11, p 314) conclude that ’Kathon CG’ is a preservative with unacceptable sensitising potential in "leave-on" products. Data from several centres (including minel) are cited in support of the view that kathon CG should be removed from these formulations. I would like to report our continued experience with kathon CG. Since June, 1984, 1378 patients have undergone patch testing at the Mayo Clinic, in standard fashion, to 0-01% aqueous kathon CG. Although initially in the standard allergen battery, since January, 1987, we have used it in our preservative series (to which the vast majority of our contact dermatitis patients are tested). Significant reactions were noted in 40 patients (2-9%). The frequencies were 3-6% (13/365) over the two years to June, 1986; 3-1% (20/655) in the period June, 1986, to October, 1987;and2-0% (7/358) from then to December, 1988. Analysis of our test results suggests that patients found to be sensitive to kathon CG tend to be older, and they often had a history of long-standing dermatitis. Almost all of these chronic dermatitis patients had been exposed to a plethora of topical prescription and over-the-counter medicaments, primarily leave-on products. Some contained kathon CG at 3-15 parts per million. Most of these patients had been referred to us after frequent consultations and treatments elsewhere. Since kathon CG is present in so many cosmetic formulations and since most patients in our series seem to have been sensitised after the onset of dermatitis, not de novo, the use by the general population of kathon CG in leave-on products at the manufacturer’s recommended use concentration seems to be safe. Unsupervised use in chronic dermatitis may be inadvisable. Our cohort should not be interpreted as indicative of the general United States public or even of patients at other contact dermatitis clinics. In the multicentre study cited by de Groot and Herxheimer the sensitivity rate for San Francisco was only 0.4%;2 there are similar unpublished data from other cities. It may be inaccurate to refer to a "high prevalence rate" for the entire United States. The explanation for the (non-significant) decrease in sensitivity over the 4 years of our study period is inapparent but I suspect that our true rate is 2-0-25%, which is perhaps acceptable in the

patients we see. Disagreement also remains over the irritant response to kathon CG, the elicitation threshold, and the response to provocative use testing (ranging from 0 to 100%). Additional experience and more detailed skin testing data may help to clarify these issues. Kathon CG has been the eighth most reactive allergen over the past 5 years at our institution, behind established preservatives such as paraben mix (4-1%), bronopol (4-5%), quatemium-15 (4-9%), and formaldehyde (7.6%); only sensitisation to imidazolidinyl urea is seen less frequently (22%). De Groot and Herxheimer are right to emphasise the need for more extensive toxicological evaluation before marketing, the importance of using preservative concentrations in the light of such an evaluation, and the need for labelling of ingredients on products to which the public may be

ANTHONY F. FRANSWAY

Fransway AF Sensitivity to Kathon CG: findings in 365 consecutive patients. Contact Dermatitis 1988; 19: 342-47. 2. Cronin E, Hannuksela M, et al. Frequency of sensitization to the preservative Kathon CG. Contact Dermatitis 1988; 18: 274-79. 1.

* Dr Herxheimer and Dr de Groot’s paper prompted a question in the European Parliament from Dr Caroline Jackson, MEP. The isothiazolinone known as ’Kathon CG’ is a permitted preservative under a 1976 EEC directive. On Feb 21, 1989, the European Commission adopted an amendment altering the maximum permitted concentration from 30 to 15 parts per million. This action was "In response to a number of isolated instances of sensitivity".ED. L. BALDNESS AND MINOXIDIL

SiR,—We would like to respond to Dr Burton’s letter (Feb 25, p 442). Upjohn Ltd is not "seeking to increase anxiety about a physiological event". The company is, however, concerned that men who are anxious about alopecia androgenetica or "male pattern baldness" should consult their physician for qualified medical advice rather than approach hair clinics for help. Clinics offer treatments that are often ineffective and expensive and which, in the absence of qualified medical supervision, could prove dangerous. The purpose of the pharmacy video is to stress that it is the patient’s physician who should be approached for an informed opinion and

professional advice on treatment of hair loss. Upjohn Ltd, Crawley, West Sussex RH10 2NJ

A. D. MITCHELL

SIR,-Dr Burton comments critically on a wall video in a father and equally worried pharmacy showing a "miserable young son", the father having male-pattern baldness. Someone had better point out to Upjohn Ltd that male-pattern baldness is not inherited through the father. A picture (though accurate) of ...

non-bald mother, I suppose, would not do. The mistake would be humorous were it not for the phenotypic anguish the company attempts to create in young men. Beaumont Clinic of Preventive and Nutritional Medicine, 390 Park,

Birmingham, Michigan 48009, USA

LINDA L. DARGA

DOPPLER ULTRASOUND AND EARLY PREGNANCY FAILURE

SIR,-Recent Lancet correspondence has considered blood velocity waveforms in uteroplacentall and umbilical2 vessels. While agreeing with the conclusions drawn, we have reservations about the method. No mention was made of the reproducibility of the observations, which can seriously affect results.3.4 Furthermore we find it important to identify precisely at which point along the uterine arterial tree the observations are made: values for resistance index at the level of the uterine artery were consistently 50% higher than those at the chorion frondosum.S We have applied the technique of pulsed doppler ultrasound to develop a normal range of resistance index in the uterine or arcuate arteries or branches in the first trimester of pregnancy. Eight women whose pregnancies had failed following threatened abortion (five), and live ectopic pregnancy (three) were also studied. Flow velocity waveforms were obtained three times 5 min apart by the same observer and the within-observer coefficient of variation was less than 5%. There was no apparent abnormality in the resistance index in the eight patients whose pregnancies had failed, although