Primary milia in older children and adults develop on the face, particularly around the eyes. Secondary milia are found anywhere on the body at the sites affected by the predisposing condition. Eruptive milia occur on the head, neck, and upper body. Milia en plaque presents as a distinct plaque in the postauricular area, either unilaterally or bilaterally. Submandibular plaques and lesions on the pinna have been reported.
Secondary lesions arise following blistering or trauma, due to disruption of the sweat duct.
Milia have been described in many disorders, including bullous pemphigoid, inherited and acquired epidermolysis bullosa, bullous lichen planus, porphyria cutanea tarda, and burns. Skin trauma from dermabrasion can result in milia formation. Radiotherapy that causes destruction of skin appendages can result in rings of milia at the periphery of the treated skin. Secondary milia have been described following potent topical corticosteroid use. Milia are a feature of a number of very rare genodermatoses.