What should you know about worst ringworm?

Ringworm is a fungal infection, not a worm. A more severe case may form several expanding, scaly rings, affect the scalp, beard, nails, or groin, or cause marked inflammation. Scratching can break the skin and allow a bacterial infection to develop. A rash that resembles ringworm can also have another cause, so appearance alone cannot confirm the diagnosis.

Ringworm can spread through skin contact, shared towels, clothing, sports equipment, or infected pets. A clinician may check the affected area and decide whether testing or prescription treatment is needed. See the overview of [Ringworm](/conditions/ringworm/) and related [Skin Rash](/symptoms/skin-rash/) or [Scaly Skin](/symptoms/skin-scaling/).

Keep the area clean and dry, wash hands after touching it, and avoid sharing towels, clothing, brushes, or sports gear. Wear loose clothing and change damp garments promptly. Do not use a steroid cream by itself on a suspected fungal rash unless a clinician specifically advises it, because it can alter the appearance and allow infection to progress. A clinician may recommend [Topical Antifungal Treatment](/treatments/medical-dermatology/topical-antifungal-therapy/) for limited skin disease or [Oral Antifungal Treatment](/treatments/medical-dermatology/oral-antifungal-therapy/) when infection is extensive or involves areas such as hair or nails.

Arrange medical care promptly if the rash is rapidly spreading, very painful, swollen, draining, warm, or accompanied by fever. Seek assessment for scalp involvement, hair loss, nail changes, a weakened immune system, or failure to improve after following treatment instructions. Urgent care is appropriate for severe facial swelling, eye involvement, or feeling acutely unwell.

Could this be ringworm or another rash? Does the location or extent call for a skin test? Which treatment is suitable, and how should household contacts, pets, towels, and clothing be managed? What change would mean the infection needs review?