Milia
Milia are small, white or yellowish bumps that appear on the skin due to the buildup of keratin beneath the epidermis, forming cysts. These clusters can occur anywhere on the body, but are most commonly found around the eyes and nose. While milia are especially prevalent in newborns—affecting up to 50% of healthy infants—they can develop in individuals of any age, particularly as skin loses its ability to shed properly with age. Unlike acne, which involves clogged pores, milia form just beneath the skin's surface and are often mistaken for acne lesions.
There are two main types of milia: primary milia, which occur spontaneously from keratin buildup, and secondary milia, which arise after skin conditions or diseases. Various types of milia exist, including neonatal milia, juvenile milia linked to genetic disorders, and multiple eruptive milia, characterized by itchy clusters. Although milia generally do not cause discomfort, they can be a source of self-consciousness. Treatment options include cryotherapy, heat treatments, deroofing, and topical retinoids, although many cases, especially in infants, resolve on their own within weeks.
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Milia
Milia are small yellow or white bumps visible on the epidermis of skin that are caused by keratin buildup just beneath the skin’s surface. A cyst forms under the epidermis that fills with keratin and creates milia. Milia refers to a cluster of cysts on the skin, while a single cyst is referred to as a milium. Milia can form on many different skin regions. Common spots on which milia form include areas around the eyes and nose. Although milia most commonly occur in newborn babies, people of all ages can develop milia. Due to their whitish/yellowish appearance, they are often confused with acne. Childhood milia often disappear after a few weeks. Adult milia usually last longer and may require removal by a dermatologist.
Background
A person’s skin is composed of three layers: the epidermis, the dermis, and the hypodermis. The outermost, visible layer of skin is called the epidermis. The epidermis is made up of skin cells called epithelial cells as well as specialized cells known as keratinocytes. Keratinocytes help protect the body from pathogens, or harmful microbes. They are composed of a protein called keratin, which has the job of holding skin cells together and anchoring it to the dermis.
Keratin is an important protein in skin cell health. Keratin is constructed from intermediate filament proteins, which are responsible for the cells’ attachment abilities. Keratin’s two main functions are to hold the skin cells together and form the outermost skin layer that protects skin from the environment. Keratin has the power to waterproof the skin. It is also integral to maintaining skin strength alongside collagen and elastin, two more important proteins that make up the skin. Keratinized skin cells are constantly growing outwards. As they build up, the outermost cells begin to die and are shed from the skin surface to make way for newer cells below the epidermal surface. The ongoing cyclical process of skin cell growth and shedding takes about five weeks in total.
Keratin can become trapped within the epidermal layer. Clogs in the epidermal layer usually occur when the skin does not shed dead layers of cells properly. Dead skin cells can become trapped beneath the surface of skin for a number of reasons, such as poor hygiene or as a result of a skin condition. Milia are very common among newborns, and up to 50 percent of healthy newborns will develop milia. Milia can occur at any age, however, and often occurs in older people because the skin loses its natural ability to shed with age.
Milia are often mistaken for acne, which occurs when the pores of the skin become clogged. Milia do not occur within pores, rather they sit just beneath the outermost skin layer and form a cyst filled with keratin. Milia often co-occur with acne and blackheads, however, although milia can occur on clear skin as well. Milia can also occur after a skin injury, such as a burn, rash, blister, or sunburn. Certain medications are also known to cause milia, including topical corticosteroids and certain chemotherapy drugs. Milia has also been linked to skin conditions that cause blistering such as epidermolysis bullosa (EB), cicatricial pemphigoid, and porphyria cutanea tarda (PCT).
Overview
Milia present as small, circular bumps on the skin’s surface that are white or yellow in color. Although they do not cause any pain or irritation, they are sometimes a source of self-consciousness for people. When irritated, milia can become red. Milia are most often found near the eyes and nose but can also develop near the lips, cheeks, torso, and genitalia. Milia that occurs spontaneously are known as primary milia, while milia that occurs after a skin disease is referred to as secondary milia. Primary milia are formed from the direct buildup of keratin, while secondary milia develop only after a skin condition or disease has clogged the skin’s surface.
Experts have identified several types of milia. Neonatal milia is a primary milia that develops in newborns. Newborns sometimes develop milia because their skin is underdeveloped and not yet able to exfoliate itself. Neonatal milia is commonly seen on the face, scalp, and upper torso and usually clears within several weeks. Certain rare genetic disorders can lead to the development of juvenile milia, in which case this type of milia is classified as secondary milia. These genetic disorders include nevoid basal cell carcinoma syndrome (NBCCS), pachyonychia congenita, Gardner’s syndrome, and Bazex-Dupré-Christol syndrome. Milia en plaque is a type of milia related to genetic or autonomic skin disorders and normally affects the ears, cheeks, eyelids, or jaw. This type of milia mainly occurs in middle-aged females and the cysts can grow to be several centimeters in diameter. Multiple eruptive milia is an eruption of itchy clusters of milia that crop up on the arms, face, and torso. This type of milia can spread across skin over several weeks or months.
Once diagnosed by a dermatologist, milia can be treated in several ways. For infants, milia usually clears on its own. For older children and adults, clearing of milia may take longer. If a person wishes to clear their skin of milia faster, they can undergo several types of treatments for removal. The most common form of treatment, cryotherapy, uses liquid nitrogen to freeze the milia off the skin. Other doctors use diathermy, or extreme heat, to destroy the cysts. Deroofing involves using a sterile needle to pierce the skin and remove the contents of the cyst. Some doctors will prescribe topical retinoids or chemical peels to exfoliate the skin in an attempt to eliminate the milia. Laser ablation uses a laser to target and destroy cysts. Some doctors simply scrape the cysts from the skin’s surface and cauterize the wounds afterward.
Bibliography
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“Keratin Protein & the Epidermis.” Study.com, 2020, study.com/academy/lesson/keratin-protein-the-epidermis.html. Accessed 11 Mar. 2020.
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