25% Undecylenic Acid: Uses, Side Effects, and Drug Interactions

# Undecylenic Acid 25% Overview Undecylenic acid 25% is a medicine used to treat fungal infections on your skin. It works by stopping the growth of fungi that cause problems like athlete's foot, jock itch, and ringworm. You apply this product directly to the affected area of your skin. It's available without a prescription, so you can buy it at most drugstores. This medicine is meant only for external use on the skin—never swallow it or put it in your eyes, nose, or mouth. When using undecylenic acid 25%, you should stop using it and talk to a doctor if your skin condition gets worse or doesn't improve after a few weeks of use. Don't use this product on children under a certain age without asking a doctor first. Keep it away from children and pets since it's not safe if swallowed. If you're pregnant or breastfeeding, check with your doctor before using this product to make sure it's safe for you. If you accidentally swallow this medicine or get it in your eyes, call poison control or a doctor right away.