Lidocaine is a local anesthetic (numbing medication). It works by blocking nerve signals in your body. Lidocaine topical (for use on the skin) is used to reduce pain or discomfort caused by skin irritations such as sunburn, insect bites, poison ivy, poison oak, poison sumac, and minor cuts, scratches, or burns. Lidocaine topical is also used to treat rectal discomfort caused by hemorrhoids. Lidocaine topical may also be used for purposes not listed in this medication guide. An overdose of numbing medicine can cause fatal side effects if too much of the medicine is absorbed through your skin.