What should you know about tinea incognito images?

After corticosteroid use, ringworm may lose its circular border and appear as a broad, uneven, faintly red or brown patch. Scale can be subtle, and bumps or pustules may occur. Lighting and skin colour affect photographs, while eczema, contact dermatitis, psoriasis, and bacterial infection can look similar. Steroid history and change over time are as useful as a single image.

Take a well-lit image without filters and record when it was taken. Show the clinician earlier images and every product used. Avoid trying several creams before review. A clinician may inspect scale or test a sample; treatment can include a topical plan or oral antifungal treatment when appropriate.

Seek review if the rash enlarges, becomes painful, develops pus, or fails to settle. Get prompt help for fever, facial or eye involvement, rapid spread, or significant swelling. A changing image is a reason to reassess, not to diagnose yourself.

What features make fungus more or less likely? Could the steroid have changed the appearance? Would testing alter treatment?