Perioral dermatitis is similar to acne and rosacea in that there is facial erythema, papular pustules, and other damage, but it occurs primarily around the mouth. Many causative factors have been proposed for perioral dermatitis, including exposure to corticosteroids and fluoride in water or ointments, but the exact etiology, however, remains unclear. It is prevalent in women and children of childbearing age. Typically, the lesions begin in the nasolabial folds and gradually spread to the perioral area and can invade the lip margin. The diagnosis is based on the fact that perioral dermatitis is not associated with acne, which distinguishes it from acne; the rosacea rash does not involve the perioral area or the periocular area, which distinguishes it from acne. Seborrheic dermatitis and contact dermatitis must be excluded before diagnosis. Dermatopathological biopsies show edema and lymphocytic histiocytic infiltration of the spiny cell layer and can affect hair follicles, which are usually clinically unnecessary. Treatment is anti-inflammatory in nature.