What causes milia? Primary and secondary causes

Milia form when keratin, the tough protein that makes up the top layer of skin, gets trapped in a tiny pocket just under the surface. What traps it differs from person to person. Most milia appear on their own with no clear trigger. Others follow something that hurt or changed the skin: a burn, a blistering disease, a strong peel, a laser, a steroid cream or a medicine. This guide lists every cause the medical sources name, and the causes people often ask about that the sources do not support. For what milia are, see the hub guide, what milia are.

Skinli gives general education and is not a doctor.

How milia form

MedlinePlus, from the U.S. National Library of Medicine, says "Milia occur when dead skin becomes trapped in small pockets at the surface of the skin or mouth." StatPearls, a medical reference hosted by the same library, gives more detail. It describes milia as "subepidermal keratin cysts," small closed cysts just under the top layer of skin, and explains where they start:

• Primary milia, the ones that appear on their own, "are considered to arise from the lower infundibular sebaceous collar of the vellus hair follicles." In plain words, from a point near the base of the fine, soft hairs that cover most of the skin.
• Secondary milia, the ones that follow damage, "are believed to derive more frequently from the eccrine ducts," the ducts of sweat glands, "than from hair follicles, sebaceous ducts, or overlying epidermis."

A 2008 review in the Journal of the American Academy of Dermatology, "Milia: a review and classification," says "there are few studies on the origin of milia." A 2020 review in the International Journal of Women's Dermatology agrees: "The exact etiology of multiple milia remains unknown." Etiology means cause.

Primary milia: the ones that appear on their own

StatPearls classifies primary milia into several types:

• Congenital milia, present at birth in "up to 40% to 50% of healthy full-term neonates." See milia in babies.
• Benign primary milia of children and adults, which "tend to occur on the eyelids, cheeks, forehead, and genitalia." This is the most common adult type, and it has no known trigger. See milia under the eyes.
• Milia en plaque, "an erythematous plaque studded with numerous milia," a red patch dotted with milia. StatPearls says its cause "is still not well understood" and that it is "more common in females."
• Multiple eruptive milia, which "emerges suddenly over weeks to months." StatPearls says it usually occurs by chance, but "can be inherited in an autosomal dominant fashion," meaning passed from one parent, or appear with certain rare skin disorders.
• Milia with inherited skin disorders. StatPearls says "a small percentage of primary milia may occur in association with certain rare genodermatoses (inherited genetic skin disorders)." A 2009 report in Pediatric Dermatology described a family whose newborn milia were "profuse and more persistent than usual," with no other health problems.

Secondary milia: the ones with a trigger

StatPearls says "secondary milia manifest in association with underlying skin pathology, medications, or skin trauma." Here is every trigger it and the other sources name.

Skin injury

• Burns, grafts, dermabrasion and radiotherapy. StatPearls says "Secondary traumatic milia most often follow burns, skin grafting, dermabrasion, or radiotherapy." Dermabrasion is a clinic treatment that sands away the top layers of skin.
• Swollen or injured skin. MedlinePlus says milia "also occur on parts of the body that are swollen (inflamed) or injured."
• Freezing treatment. A 2014 report in Dermatology Online Journal describes milia at a site treated with liquid nitrogen, which "develop at a healed liquid nitrogen cryotherapy site."
• Repeated friction. A 2025 report in Cureus describes a patch of milia on the forehead of a 67-year-old man "at the site of chronic mechanical friction from prayer-related prostration," from years of touching the forehead to the ground in prayer.
• Tattoos. A 2017 report in the Journal of Drugs in Dermatology describes "tiny, white papules confined within the margins of a tattoo," and says only three earlier reports existed.

Clinic procedures

• Chemical peels. A 2005 review in the Journal of Cosmetic Dermatology says medium-depth peels sometimes lead to complications including dark or light patches, redness, raised scars, infections "and milia."
• Laser resurfacing. A 1997 paper in Plastic and Reconstructive Surgery, from surgeons who had treated almost 2,100 patients, lists "acne, milia, dermatitis, and infection" among "Common problems" after CO2 laser resurfacing, and says they "can be controlled or avoided with proper postoperative care."

The guide exfoliating acids for milia covers what this means for home products.

Blistering diseases

StatPearls says milia "may manifest after the clearing of inflammatory skin diseases as sequelae of bullous disorders," meaning as an after-effect of blistering diseases. It names porphyria cutanea tarda and epidermolysis bullosa. The 2020 review lists "hereditary forms of epidermolysis bullosa, epidermolysis bullosa acquisita, bullous pemphigoid, bullous lichen planus, and porphyria cutanea tarda." The American Academy of Dermatology (AAD), on epidermolysis bullosa, says milia are "Tiny, white bumps on the skin" that "may appear when the blisters disappear."

Medicines and skin reactions

• Steroid creams on thinned skin. StatPearls says medication-related milia "appear with chronic topical steroid use in atrophic skin," meaning long-term steroid creams on skin that has become thin.
• Anti-inflammatory pills. StatPearls also names "nonsteroidal anti-inflammatory drugs," the group that includes ibuprofen.
• Isotretinoin. A 2026 report in Cureus describes milia under the eyes of a teenager two months into isotretinoin for acne, and calls this "a rare side effect."
• Allergic skin reactions. A 1996 report in Contact Dermatitis is titled "Milia as unusual sequelae to allergic contact dermatitis." A 2003 report is titled "Milia complicating photocontact allergy to absorbent sunscreen chemicals," an allergic skin reaction to sunscreen chemicals that involves sunlight. Both describe single cases.

Causes people ask about that the sources do not support

• High cholesterol. None of the sources links milia to cholesterol. The yellow eyelid patches that are linked to blood fats are xanthelasma. StatPearls describes them as "soft, lipid-rich deposits, particularly cholesterol," and estimates that 50 percent of adults with xanthelasma have abnormal blood fat levels. The guide white bumps that are not milia covers this and other lookalikes.
• Stress, diet, hormones, dry skin, heavy creams or vitamin deficiency. None of the sources read for this guide names any of these as a cause of milia.
• Poor hygiene. No source links milia to cleanliness. Milia form under the surface, inside the skin.
• Infection. Milia are cysts, and no source describes them spreading between people. Molluscum contagiosum, a bump that can look like milia, is a viral infection that MedlinePlus says spreads through contact.

Can milia be prevented?

MedlinePlus says "There is no known prevention." Some triggers can be avoided or planned for. Protect healing skin after burns and procedures, and ask the doctor who does a peel or laser about aftercare, since the 1997 paper says milia after resurfacing can be "controlled or avoided with proper postoperative care." Do not use steroid creams on the face for long periods unless a doctor tells you to. Do not pick at bumps, which injures skin.

What to tell your doctor

The cause of milia is found from your history more than from a test. StatPearls says milia "are diagnosed on clinical findings," by looking, and that in older age groups a doctor considers inherited conditions and skin injury "based on other historical and clinical findings." Before the visit, write down:

• When the milia appeared, and whether they came all at once or one by one.
• Any burn, blister, rash, injury, tattoo or piercing in that area.
• Any peel, laser, freezing treatment or dermabrasion, and when.
• Every cream you use there, especially steroid creams, and for how long.
• Every medicine you take, including isotretinoin and anti-inflammatory pills.
• Whether anyone in your family had many milia, or blistering skin.
• Any other symptoms, such as blisters, fragile skin, cough or tiredness.

When the cause needs a doctor

StatPearls says "persistent and widely distributed milia may require investigation for other causes of primary and secondary milia, such as an underlying genodermatosis." See a dermatologist if many milia appear at once, if milia follow blisters, if they appear in an older child, or if they keep returning. A 2025 report in BMJ Case Reports described eyelid milia as the only eye sign of sarcoidosis, a disease that can affect the lungs, lymph nodes and skin, so new milia with other symptoms are worth a full check. To tell milia from whiteheads, see milia vs whiteheads.