Inverse psoriasis (also known as intertriginous [in-ter-TRIJ-uh-nus] psoriasis) appears on skin of color as lesions of purple-ish, brown, or darker than the surrounding skin, in body folds. On Caucasian skin, it appears as bright red lesions in body folds. It may appear smooth and shiny. Many people with inverse psoriasis have another type of psoriasis elsewhere on the body at the same time.
Inverse psoriasis is found in the armpits, groin (including the genitals), under the breasts, and in other skin folds on the body. Rubbing and sweating can further irritate inverse psoriasis because of its location in skin folds and tender areas. It usually lacks the scale associated with plaque psoriasis due to the moist environment. Inverse psoriasis is more common in overweight people and those with deep skin folds.
Common triggers for inverse psoriasis include:
- Certain medicines
- Starting and stopping medicines
- Injury to the skin
- Tobacco or alcohol use
- Friction on deep skin folds