What to put on an underarm rash

Dry irritation and a damp fold need different care

Contact dermatitis means inflammation caused by something touching your skin. Deodorant fragrance or preservatives, soap, excessive washing and friction can trigger an underarm rash. Dryness, itching, cracking or burning can fit contact dermatitis. Intertrigo means inflammation in a skin fold, where heat, moisture and rubbing damage the skin. The fold can become moist, raw or cracked, and sometimes develops a fungal or bacterial infection. These clues overlap, so appearance alone is not enough to choose an infection treatment.3456

What to do first

1. 1Remove the likely trigger. Stop a deodorant, soap or other product that seems linked to the rash. Rinse away any remaining irritant with plenty of water.
2. 2Choose care for the skin's condition. For a sweaty, rubbing fold, dry thoroughly, using a hairdryer on cool if needed. Wear loose clothing and separate rubbing surfaces with clean gauze or a dry towel.
3. 3Apply the appropriate plain product. For dry contact irritation, test a fragrance free moisturiser on a small area before wider use, then apply after washing while the skin is still damp. Reapply when dry. For friction in the fold, use petroleum or zinc oxide cream or ointment as a barrier.
4. 4Soothe itching with a clean, cool, damp towel for 10 to 15 minutes a few times daily. Avoid scratching, which can worsen the rash and lead to infection.

Adding products is not the same as removing a trigger, however impressive the bathroom shelf looks. A reaction can appear hours or days after exposure, and a product you have used for years can still become a problem. Antiperspirant can reduce sweating, but it can also cause dryness and irritation; do not use it to manage moisture if it is causing the rash.134

Do you need hydrocortisone or an antifungal?

Hydrocortisone reduces inflammation and itching; antifungals such as clotrimazole treat yeast or fungal infection. An underarm rash is not automatically fungal just because it is in a warm, moist place. Choosing a cream by its purpose is more useful than choosing by how many promises fit on the tube.246

For contact dermatitis, 1% hydrocortisone is an option for itch relief. Use topical steroids only for short periods and do not exceed the frequency your clinician advises. Stronger steroid creams are best avoided in underarm folds because they can thin the skin. If infection is suspected, get medical advice rather than treating inflammation alone. Bacterial infections need a different treatment from fungal infections.1245

Do not assume an antibiotic ointment is a neutral addition: topical antibiotics such as neomycin can themselves cause contact allergy. A clinician can examine the rash and, when needed, take a scraping or swab to identify an infection.45

How long should it take to improve?

Contact dermatitis clears in 2 to 3 weeks in most cases, but can return if the trigger remains. A rash can persist for weeks after exposure stops. For a damp fold rash, seek care if good home care does not clear it or it spreads beyond the fold. Persistent, recurring or severe symptoms also need assessment; repeated contact dermatitis sometimes needs patch testing to identify the allergen.235

When to get medical help promptly

Seek immediate medical advice for rapidly worsening symptoms, increasing pain, discharge, feeling unwell, or feeling hot, cold or shivery. Pus filled bumps, tender raised bumps or a foul smell also need prompt assessment. Diabetes or a weakened immune system increases the risk of intertrigo, including infection, so mention either when seeking care.467