Milia are very common, benign, keratin-filled cysts that occur in patients of all ages, from infancy upward.
Primary milia arise in infants most commonly, but also can occur in children and adults.
Secondary milia are seen in a number of blistering disorders and following dermabrasion. Milia are tiny epidermoid cysts. The cysts may be derived from the pilosebaceous follicle. Primary milia arise on facial skin bearing vellus hair follicles. Secondary milia result from damage to the pilosebaceous unit.