What should you know about Wood's lamp test for ringworm?

Ringworm is a fungal infection of skin, hair, or nails. When the suspected area is examined in a dark room, some fungi may produce a visible fluorescence, while others show no distinctive glow. A non-fluorescent result therefore does not rule out ringworm. The clinician also considers a circular or expanding rash, a raised scaly edge, hair changes, the body site, and contact history.

Surface products and the natural colour of skin can affect visibility. If the pattern is uncertain, a clinician may gently collect scale or hair for laboratory examination. The lamp is an aid to diagnosis, not a test that identifies every fungal species or separates every rash from ringworm.

Keep the area clean and dry, avoid sharing towels or clothing, and wash items that touch the affected skin as advised. Do not use a steroid cream alone on a suspected fungal rash unless a clinician specifically directs you, because it can change the appearance. Treatment may involve [Topical Antifungal Treatment](/treatments/medical-dermatology/topical-antifungal-therapy/) or, when the site or extent requires it, [Oral Antifungal Treatment](/treatments/medical-dermatology/oral-antifungal-therapy/). A [Skin Rash](/symptoms/skin-rash/) or [Scaly Skin](/symptoms/skin-scaling/) page can help describe what you notice.

Seek medical care when a rash involves the scalp, beard, nails, eyes, or a child, or when it is spreading despite treatment. Prompt review is appropriate for pus, severe pain, facial swelling, fever, or a weakened immune system. Contact the clinic if the lamp result and the visible rash do not seem to match.

Ask whether the pattern is consistent with ringworm, whether a scraping or hair sample is needed, how long to use the recommended medicine, and how to reduce spread to household members.