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Clinician’s Corner: Sweat Rash (Tinea versicolor)

The very warm weather we have been experiencing saps the energy right out of us! However, the fungus that causes Tinea versicolor gets “supercharged” and grows more rapidly in this heat and humidity. Tinea versicolor often referred to as “sweat rash” caused by Malassezia furfur a fungus that normally grows on our skin.

With the heat and humidity, as well as oily skin, this organism can overgrow on our skin, especially where it is warm, dark and moist.  Look around shirt collar lines, under bra’s, the folds of skin, armpits etc. and you will see these flat discolored lesions. These lesions don’t change colors with sun exposure; they are lighter in the summer than surrounding skin, and darker in the winter. The lesions will glow yellow/green when exposed to a “black light”.


  • Selsun (selenium sulfide 2.5% shampoo (Rx only). Over the counter is not strong enough.

Directions: Apply a thin layer covering the body surface from the face to the knees once daily for seven days. Leave on skin for five to ten minutes before rinsing. Remove jewelry before application, as it may damage jewelry.

Disadvantages: odor of the product which smells like rotten eggs.

You may experience a stinging sensation after application

  • Head and Shoulders shampoo (OTC): applied once daily, leave on for 5 minutes.  Apply daily for 2 consecutive weeks.
  • Nizoral® ketoconazole 2% shampoo (Rx) single application for five to ten minutes is effective (80% mycotic cure rate). May be applied up to 3 days.
  • Topical antifungal creams: usually applied daily for 14 days. Examples: Clotrimazole (Lotrimin-OTC) Miconazole (Micatin-OTC), Ketoconazole (Nizoral-Rx)
  • Oral Treatment of tinea versicolor (Rx only) :
    • Fluconazole 400mg as a single dose. Exercise to a sweat, and do not shower for 12 hours.
      • Alternative: 300mg once a week for 2 consecutive weeks (75% cure rate)
      • Other prescription medications due to effectiveness or side effects should not be used.

Relapse rates: Because the fungus that causes tinea versicolor is part of the normal skin,  60% of cases relapse one year after treatment, and 80% relapse after two years.  Prevention (especially in warm weather) use selenium sulfide 2.5% or ketoconazole 2% shampoo applied to the entire body for ten minutes once per month is an effective to prevent the rash from coming back.

Your Thompson Pharmacist is your best source for all your summer time ailments.   Go ahead and ask—at Thompson Pharmacy it’s all for YOU!