For genital warts: Redness, wearing away of skin, flakiness & swelling, hardening under the skin, small open sores, crust that forms during healing, blisters, itching, burning sensation or pain in the treated area; headache. For basal cell carcinoma: Slight itching; paresthesia, small swollen areas in the skin, pain, burning, irritation, bleeding, redness or rash, swollen glands & back pain. For actinic keratosis: Slight itching; pain, burning, irritation or redness, headache, anorexia, nausea, muscle pain, joint pain & tiredness.