A 25-year-old girl having androgenetic alopecia developed itching and erythema on the scalp one month after she started applying a commercial preparation containing 2% minoxidil. The dermatitis disappeared on discontinuing minoxidil but recurred when she applied minoxidil again after a gap of 1 month. Patch tests revealed a papulovesicular reaction with the commercial minoxidil lotion and also with a minoxidil tablet powdered and made into a paste with distilled water. Patch tests with ethyl alcohol were negative.

INTRODUCTION

Topical minoxidil was first used for alopecia areata in 1981_1,2 and subsequently for androgenetic alopecia as well._3-6 It is a fairly safe drug except that a proportion of the topically applied drug gets absorbed through the skin and if the quantity of the drug applied is more, it can cause headache in the patient. This headache is dose dependent and disappears if the quantity of the drug applied on the skin is reduced. The other side effects include a mild irritant dermatitis and increased hair growth in regions outside the area of drug application. Contact dermatitis due to minoxidil has been reported in eight cases._2,7-10 All these cases were confirmed by positive patch test reactions with minoxidil. One patient of Tosti et al9 had photoallergic contact dermatitis.

In India, topical minoxidil was first introduced in 1988, but contact dermatitis due to minoxidil has not been reported so far. We are reporting, the first Indian case of contact dermatitis due to this drug confirmed by patch tests.

Case Report

One and half years ago, a 25-year-old girl started having diffuse loss of hair from the fronto-parietal areas of her scalp for which in August 1990, she started applying a commercial hair lotion containing 2% minoxidil in an alcoholic base. One month after the start of the treatment, she noticed itching and erythema in the corresponding areas of the scalp, and this became worse with further applications. A general practitioner advised her to stop further applications of minoxidil and prescribed betamethasone 17-valerate topically and antihistamines orally. The lesions subsided in 3 days. One month later, the patient applied the minoxidil lotion once again and developed dermatitis within 3 hours, but the same treatment again led to regression of the dermatitis.

In May 1991, she consulted us for advice regarding her hair loss. She had no recurrence of dermatitis ever since she stopped applying minoxidil. A standard occluded patch test with the commercial minoxidil lotion showed a severe papulovesicular reaction. A similar reaction was obtained with the commercial minoxidil lotion used in the specialized cup designed by us for testing volatile substances. A milder reaction was obtained in the patch test undertaken with a tablet of minoxidil powdered and wetted with distilled water. Patch tests with ethylalcohol were negative.

Comments

Excessive applications of minoxidil lotion can sometimes cause non-specific irritant reactions, but contact dermatitis should be suspected if the patient reacts to normal or even smaller quantities of the drug.

It is also necessary to exclude the possibility of contact hypersensitivity to some other constituent of the commercial solution rather than minoxidil itself. The commercial minoxidil solution contains propylene glycol and ethyl alcohol as a base for minoxidil and at least 4 patients have been recorded who were actually allergic to propylene glycol rather than minoxidil.7,10,11 Contact hypersensitivity to alcohol is also well documented12 Positive patch tests in our patient with the powdered tablet of minoxidil leave no doubt that our patient had contact hypersensitivity to minoxidil itself and not any other ingredient.

References

1. Weiss VC, West DP, Mueller CE. Topical minoxidil in alopecia areata. J Amer Acad Dermatol. 1981; 5:224-226.
2. Weiss VC, West DP, Fu TS et al: Alopecia areata treated with topical minoxidil, Arch Dermatol 1984; 120: 457-463.
3. De Villez RL: Topical minoxidil therapy in hereditary androgenetic alopecia, Arch Dermatol 1985; 121: 197-202.
4. Katz HI, Hien NT, Prawer SE et al: Long-term efficacy of topical minoxidil in male pattern baldness, J Amer Acad Dermatol 1987;16:711-718.
5. Rietschel RL and Duncan JH: Safety and efficacy of topical minoxidil in the management of androgenetic alopecia, J Amer Acad Dermatol 1987;16:677-685.
6. De Villez RL: The therapeutic use of topical minoxidil, Dermatol Clin 1990;8:367-375.
7. Degreef H, Hendricks 1 and Dooms-Goossens A: Allergic contact dermatitis to minoxidil, Contact Dermatitis 1985;13:194.
8. Fiedler-Weiss VC, West DP, Buys CM et al: Topical minoxidil dose-response effect in a alopecia areata, Arch Dermatol 1986;122:180-182.
9. Tosti A, Bardazzi F, De Padova MP et al: Contact dermatitis to minoxidil, Contact Dermatitis 1986; 13:275-276.
10. Van der Willigen AH, Dutree-Meulenberg ROGM, Stolz E et al: Topical minoxidil sensitization in androgenic alopecia, Contact Dermatitis 1987;17: 44-45.
11. Fisher AA: Use of glycerin in topical minoxidil solutions for patients allergic to propylene glycol, Cutis 1990; 45:81-82.
12. Pasricha JS and Verma KK : Contact dermatitis caused by ethyl alcohol, Ind J Dermatol Venereol Leprol 1990; 56:328-329.