What causes allergic rashes under the armpits?

Under normal circumstances, red rashes caused by allergic reactions in the armpit may be due to keratosis pilaris, sweat irritation, folliculitis, eczema, or dyshidrotic eczema. If any abnormalities occur, it is recommended to seek medical attention promptly. Specific analyses are as follows:

1. Keratosis Pilaris

Keratosis pilaris is a natural phenomenon occurring during the skin's metabolic process. However, some individuals may experience thickening of the keratin layer around hair follicle openings due to factors such as genetics or hormonal changes, leading to clogged pores and inflammatory reactions. Regular exfoliation and using skincare products containing salicylic acid or urea can help soften the keratin and promote normal shedding of the stratum corneum.

2. Sweat Irritation

Sweat contains substances such as salt and lactic acid. When sweat remains trapped in the armpit area, these components can irritate the skin, especially in individuals with sensitive skin, potentially causing red rashes. Additionally, friction from clothing can exacerbate this irritation. Keeping the armpits dry, changing clothes frequently, and using fragrance-free, gentle skincare products are recommended.

3. Folliculitis

Folliculitis occurs when hair follicles become infected by bacteria such as Staphylococcus aureus, triggering an inflammatory response that results in red rashes in the armpit, often accompanied by pustules and pain. Treatment under a doctor's guidance may include topical medications like mupirocin ointment, oral antibiotics such as cefuroxime axetil tablets, or fusidic acid sodium ointment.

4. Eczema

Eczema develops due to a combination of genetic, environmental, and immune factors that compromise the skin’s barrier function, leading to inflammation. Symptoms include red rashes, erythema, papules, vesicles, and erosion. Treatments may include topical corticosteroids such as desonide cream or hydrocortisone cream, or calcineurin inhibitors like tacrolimus ointment, used as directed by a physician.

5. Dyshidrotic Eczema (Sweat Blisters)

In hot and humid environments, impaired sweat expulsion can cause sweat to accumulate beneath the skin, forming small blisters that lead to rashes, itching, and stinging sensations. Keeping the armpits clean and dry, and using products such as talcum powder, can help alleviate moisture and sweating.

It is advisable to maintain good skin hygiene in daily life, perform basic skincare routines such as moisturizing and sun protection, and thereby reduce the risk of developing skin conditions.