Understanding everything about milia.

The milium cysts, also known as "milia" in English, are small white subcutaneous microcysts, generally 1 to 3 mm in diameter, formed by an accumulation of dead cells and cellular debris such as keratin.

They are not painful and are benign. Milia can appear in isolation or in clusters of around fifty small lesions. These present visually as small white bumps on the skin, often firm to the touch. They are sometimes described as small fat balls on the face, although their content is not made up of lipids, but primarily of keratin.

Situated in various areas of the face, milia can be found around the eyes, on the nose, the forehead or the chin. It is particularly common to observe a milium under the eye, an area where the skin is thin and where these microcysts appear more readily. They can also be seen on the ears, eyelids or cheeks. All age groups may develop them, although infants remain the most affected.

Good to know : Milia differ from whiteheads in their content: unlike whiteheads, milia contain neither sebum nor bacteria.

Milia are classified into two main categories:

• Primary milia : These lesions appear spontaneously. They may be congenital (affecting 40 to 50% of newborns), involving the face and scalp and resolving within a few weeks or months. Primary milia in children and adults are, by contrast, more commonly located on the cheeks, eyelids and forehead. Finally, cases of milia en plaque have been reported, a rare condition characterised by erythematous plaques containing numerous milia on the head and neck.

• Secondary milia : These cysts arise following various processes and appear over time. They represent a localised form that may be associated with a disease, a medication or a trauma, such as a skin abrasion or a second-degree burn. In very rare cases, secondary milia may be linked to conditions such as contact dermatitis, Sweet’s syndrome or phototoxic reactions.

Milial seeds appear when keratin, a protein naturally present in the skin, becomes trapped beneath the epidermis. Normally, dead cells resulting from skin renewal are gradually eliminated at the surface of the skin. However, when this process is disrupted, they may accumulate in a small superficial cyst, forming these small white bumps often observed on the face. Several factors can explain this phenomenon, depending on whether it involves primary or secondary milia. Blockage of hair follicles may in particular be promoted by the use of rich, greasy products, or may have a genetic origin, as research has revealed cases of milia associated with skin disorders such as genodermatoses.

As for secondary milia, several factors may be involved:

• Cutaneous trauma : Milia can appear after damage to the skin, such as a burn, an abrasion or repeated friction, for example following intensive use of brushes or exfoliating tools. These microtraumas disrupt the healing process: fragments of epithelium may then remain trapped in the skin, promoting the formation of microcysts.

• Exposure to UV rays : Excessive exposure to the sun can also disrupt cellular renewal and the structure of the skin. UV radiation thickens the stratum corneum and interferes with natural desquamation, which may promote the appearance of white bumps on the face.

• Prolonged application of topical corticosteroids : Prolonged use of creams containing corticosteroids can weaken the skin. These molecules can lead to alterations in the collagen and elastic fibres surrounding the hair follicles, which may promote the formation of milia. However, scientific data on this association remain limited.

• Dermatological conditions : Certain skin diseases may also be associated with the appearance of milia. This is particularly the case with epidermolysis bullosa, a condition characterised by extreme skin fragility and abnormal healing. During the skin repair process, keratin-filled microcysts can form, giving rise to secondary milia.

Although they do not present any danger, milia can be considered unsightly by some individuals.

In general, “milia” resolve spontaneously within a few weeks to a few months. However, they may persist for longer in the case of secondary milia. Several options are then available to help them disappear more quickly.

Mechanical extraction of milia.

The extraction of a milium cyst must be carried out by a healthcare professional, usually a dermatologist or a medically trained aesthetic practitioner experienced in this procedure. After disinfecting the skin, the specialist performs a very superficial micro-incision using a sterile needle or a lancet in order to open the microcyst. The keratin-filled content is then gently expelled using a comedone extractor, a small dermatological curette or a cotton bud. This technique is quick and generally only mildly painful when the lesion is superficial.

Topical application of retinoids.

Topical retinoids , such as tretinoin or adapalene, may be prescribed in certain situations, particularly in cases of multiple milia or milia en plaque. These vitamin A derivatives stimulate cell turnover and promote desquamation of the stratum corneum. By accelerating the elimination of dead cells, they can gradually clear the keratin plug and allow the microcyst to resolve.

Cryotherapy.

Cryotherapy involves applying liquid nitrogen at very low temperature to the lesion. The intense cold causes controlled destruction of the superficial skin cells. Dermatologists generally use a cotton swab or a cryogenic spray to target the milia precisely. After treatment, the area may become slightly red or form a small scab before the skin regenerates.

CO₂ laser ablation.

The CO₂ laser is sometimes used when milia are numerous or resistant to other methods. This laser emits light that is absorbed by the water contained in skin cells, allowing very precise vaporisation of the superficial layer of the epidermis where the microcyst is located. The heat produced also stimulates collagen production, which promotes skin regeneration after the procedure.

Electrodessication.

The technique of electrodessication is based on the use of a fine conductive needle connected to a low‑intensity electric current. When this needle is applied to the keratinised centre of the milium, the heat generated induces coagulation and destruction of the microcyst. The lesion then dries out and falls off within a few days.

Antibiotics.

In certain specific cases, particularly when milia are associated with skin inflammation or a dermatological condition, drug treatment may be considered. Antibiotics such as minocycline have sometimes been used. However, their use is now limited: since June 2012, the use of medicines containing minocycline for the treatment of acne has been discouraged because of the risk of allergic skin reactions. Any prescription must therefore be discussed with a doctor.

Let us recall that these techniques must be carried out by professionals. Piercing a milium cyst yourself risks causing scarring and infections by bacteria, fungi or viruses, especially when hygiene and sterilisation rules are not followed.

• MONASH S. Formation of milia following abrasive treatment for post-acne scarring. Archives of Dermatology (1953).

• TSUJI T. Milia induced by corticosteroids. Archives of Dermatology (1986).

• AL-SABAH H. & al. Milia en plaque: a new site. International Journal of Dermatology (2000).

• BERK D. R. & al. Milia: A review and classification. Journal of the American Academy of Dermatology (2008).

• BARBAROT S. & al. Les grains de milium de l’enfant. Annales de Dermatologie et de Vénéréologie (2009).

• NOTO G. Milia en plaque. Dermatological Cryosurgery and Cryotherapy (2016).

• GALLARDO AVILA P. & al. Milia. StatPearls (2023).