Undecylenic acid topical (for the skin) is a fatty acid that works by preventing fungus from growing on the skin.

Undecylenic acid topical is used to treat skin infections that are caused by fungus, such as athlete's foot, jock itch, diaper rash, prickly heat, excessive sweating in the groin area, itching, burning, and chafing.

Undecylenic acid topical may also be used for other purposes not listed in this medication guide.

Do not use undecylenic acid topical if you have had an allergic reaction to it in the past.

Do not use undecylenic acid topical on a child without a doctor's advice.

Do not cover treated skin areas with adhesive bandages or dressings that do not allow air to get through. You may use a light cotton-gauze dressing to protect your clothing from the medicine.

Avoid wearing tight-fitting, synthetic clothing (such as nylon) that doesn't allow air circulation. Wear clothing made of loose cotton and other natural fibers until the infection is healed.

Use this medication for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared.

It may take up to 4 weeks before your symptoms improve. For best results, keep using the medication as directed. Talk with your doctor if your symptoms do not improve after 2 to 4 weeks of treatment.

Do not use undecylenic acid topical if you have had an allergic reaction to it in the past.

It is not known whether undecylenic acid topical could be harmful to an unborn baby if you use the medication during pregnancy. Do not use undecylenic acid topical without telling your doctor if you are pregnant.

It is not known whether undecylenic acid passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

Do not use undecylenic acid topical on a child without a doctor's advice.