- Milia are 1–2 mm superficial white dome-shaped papules containing keratin
- Primary milia arise in neonates (50%), adolescents and adults; they are rarely familial and sometimes eruptive.
- Primary milia occur on eyelids, cheeks, nose, mucosa (Epstein pearls) and palate (Bohn nodules) in babies; and eyelids, cheeks and nose of older children and adults.
- Transverse primary milia are sometimes noted across nasal groove or around areola.
- In milia en plaque, multiple milia arise on an erythematous plaque on face, chin or ears.
- Secondary milia arise at the site of epidermal repair after blistering or injury, eg epidermolysis bullosa, bullous pemphigoid, porphyria cutanea tarda, thermal burn, dermabrasion.
- Secondary milia are reported as an adverse effect of topical steroids, 5-fluorouracil cream, vemurafenib and dovitinib.