What should you know about armpit ringworm?

Despite its name, it is caused by fungi rather than a worm. Because several underarm rashes can look similar, an uncertain diagnosis is worth checking with a pharmacist, GP, or dermatologist.

Ringworm may form a round or curved patch with a scaly, raised edge that gradually extends outward. It can itch, feel irritated, or look dry. On brown or black skin, redness may be subtle and the affected area may instead appear darker, grey, purple, or otherwise different from nearby skin.

Warmth, moisture, sweat, and rubbing in the underarm can blur the classic ring shape. Eczema, irritation from deodorant, bacterial infection, and other fungal or yeast rashes can resemble it, so appearance alone does not always settle the cause.

Keep the underarm clean and dry, pat rather than rub after washing, and choose loose, breathable clothing while the skin heals. Do not share towels, clothing, or razors, and wash your hands after touching the rash to reduce spread to other skin or other people.

A pharmacist or clinician may recommend a topical antifungal for uncomplicated ringworm on the skin. Apply it exactly as directed and continue for the full instructed course, even if the patch begins to look better. Avoid using a steroid cream on a rash that may be ringworm unless a clinician specifically advises it, because steroids can worsen or disguise the infection. Oral antifungal medicine is reserved for situations a clinician assesses, such as extensive or difficult-to-clear infection.

Arrange a clinical assessment if the rash is spreading, severe, painful, draining fluid, repeatedly returning, or not improving with correctly used antifungal treatment. Seek advice early if you have diabetes, reduced immunity, take medicines that suppress immunity, are pregnant, or are treating a young child.

Prompt care is appropriate if redness rapidly expands, the area becomes hot and very tender, you develop fever, or you feel generally unwell; these features can point to a bacterial infection or another problem needing examination. A clinician may inspect the skin and take a gentle scraping when the diagnosis is unclear.

Ask whether the rash needs a skin scraping, which antifungal form suits a moist skin fold, how long to use it, and which products should be avoided. Mention recent rashes elsewhere on your body, contact with someone or a pet with ringworm, shared sports equipment or towels, recent travel, and any steroid cream already applied.