A milium (plural milia) is a small round cyst on the skin and is filled with the skin protein keratin.
They are usually pin-point to 1-2mm in diameter, pearly white or light yellow colored smooth round bumps. Milia can develop anywhere on the body but are most common on the face (around the eyes, cheeks, forehead). Milia can develop in people of all ages and ethnicities. There are two main types of milia:
- Primary milia usually occur on the face, especially the nose, of newborn babies. They can be found in up to half of all infants. This type of milia can also be found on the gums (Epistein pearls) and the roof (Bohn nodules) of the mouth of babies.
- Secondary milia develop after injury to the skin and can develop anywhere on the body at the site of injury.
Primary milia are due to plugging of the pilosebaceous glands, which are made of hair follicles and oil glands. This happens where the glands are not fully developed, which can explain why they are found mainly in newborn infants.
Secondary milia are due to damage of the pilosebaceous glands, are are linked to many disorders and events that result in trauma to the skin, such as:
- Blistering disorders: bullous pemphigoid, cicatricial pemphigoid, porphyria cutaneous tarda, acquired and inherited epidermolysis bullosa
- Burns: heat, chemical and sun burns
- Skin procedures: dermabrasion, chemical peels, resurfacing lasers, and tattoos
There have also been reports of multiple milia suddenly developing after cancer treatment with medications such as vemurafenib and dovitinib.
Milia are typically not symptomatic and not harmful. They do not need to be treated unless they become itchy, painful, or unsightly. They can be treated in several ways by a qualified health professional:
- Retinoids: Retinoids may be helpful when there are several or widespread milia.
- Unroofing and extraction: Milia can be unroofed using a sterile needle, and the keratin content can be extracted out.
- Cryotherapy: The lesion can be frozen using liquid nitrogen.
- Electrosurgery: The lesions can be burned with electricity that is delivered through a needle tip.
- Chemical peels, resurfacing lasers, and dermabrasion may be effective when there are multiple milia. However any trauma to the skin may cause more milia to develop.
1. Bolognia JL, Jorizzo JL, Schaffer JV, eds. Dermatology. Elsevier Limited; 2012.