Ringworm (Tinea corporis) is usually treated with over-the-counter antifungal creams or powders such as clotrimazole, miconazole, or terbinafine, which work by killing the fungus and stopping it from spreading on the skin. Among these, terbinafine often works fastest, while clotrimazole and miconazole are also effective but may take slightly longer. Treatment should be applied for 1–2 weeks (and continue for at least 1 week after the rash clears) to prevent recurrence. You should see a doctor if the infection does not improve after 1–2 weeks, spreads, becomes severe, or affects the scalp, nails, or large areas, as prescription antifungal medication may be needed.