What Causes Blister-Like Scabs to Form Under the Armpit?

Blister-like scabs in or near the armpit are commonly caused by conditions such as allergic contact dermatitis, psoriasis, yeast infection and skin tagging, according to WebMD. Since each of these conditions has a different underlying cause, they each require a different type of treatment.

Allergic contact dermatitis occurs when the skin in the armpit has an allergic reaction to a substance such as a soap or type of fabric, per WebMD. This allergic reaction can result in skin irritation and blistering.

Psoriasis is an autoimmune disorder where the immune system attacks the skin cells, resulting in scaly plaques that can form in the armpits and other areas, according to the Mayo Clinic. Treatments typically involve topical creams, medication and phototherapy. However, there is no known cure as of 2015.

Candidasis is a type of yeast infection that thrives in moist areas of the skin, reports WebMD. This makes the armpit an ideal target. White scabs or plaques are a common side effect. The condition is commonly treated with antifungal medications and steroid creams, according to the University of Maryland Medical Center.

Skin tags are also known as acrochordons, states WebMD. These excess skin growths are frequently found in the armpits and on the neck, especially in older patients. The skin tags are harmless.