Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Stop using this medicine and call your doctor at once if you have:
severe burning or stinging of treated skin; or
any new skin symptoms.
Common side effects may include:
irritation of treated skin.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Undecylenic acid topical side effects (more detail)
