What is Extina? Extina (ketoconazole) is an antifungal medication that prevents fungus from growing on your skin. Extina Foam is used on the skin (topical) to treat a skin condition called seborrheic dermatitis in patients 12 years of age and older. Seborrheic dermatitis can cause areas of flaky skin (scales) on the scalp, face, ears, chest or upper back.