What Are Milia?

Milia are temporary small round lumps, known as cysts, present under the skin. They are common and can show in a plethora of ways in different areas of the skin. However, milia are commonly found on the face, often on the nose or cheeks.

Milia (singular: milium) are seen in about half of newborns. They are benign, meaning they are non-cancerous and present no clinical relevance. For this reason, milia are usually not intervened upon when noticed by the clinician, as in the majority of cases will self-resolve in around 30 days without leaving any sequelae such as scars.

Milia develops when a protein called keratin becomes trapped under the skin, thus becoming a cyst. Keratin is typically found in skin, hair and nails. These cysts can occur to anyone, regardless of ethnicity or age, but are usually found in newborns. 

Causes of Milia

In newborns

The exact cause for milia developing in newborns is not fully known to this date. It is common for milia to be mistaken for baby acne. However, it is important to differentiate the two. Baby acne causes local swelling and redness, whereas milia does not. Furthermore, babies are not born with baby acne as it will appear over time, unlike milia which are present when the baby is born.

In adults

When discussing the causes of milia in adults, there are several potential causes, including but not limited to the following:

• Associated skin conditions which can cause blistering of the skin
• Injuries which can cause blistering of the skin (such as poison ivy)
• Burns
• Sun damage
• Prolonged use of steroid cream^1,2

Classification of milia

The most widespread type of milia - primary congenital milia, manifests at birth. Milia are almost always asymptomatic and will resolve on their own within the first months of life. However, this can change according to subtypes.

Some types of milia, which are acquired may persist if treatment is not sought.³ 

Primary milia

• Congenital
• Benign primary milia of children and adults
• Milia en plaque
• Nodular grouped milia
• Multiple eruptive milia 
• Nevus depigmentosus with milia
• Genodermatosis-associated

Secondary milia

• Disease-associated
• Medication-associated 
• Trauma-associated³

Diagnosis of milia, including physical examination by a dermatologist

Milia which are congenital usually occurs without a cause and can happen at any time. On examination, small bumps, usually under 3mm in diameter, are noticeable on the skin. These bumps are off-white to yellow colour, sometimes also showing a slight tint of blue in darker skin complexions. 

They are smooth and dome-shaped. Milia sometimes presents as solitary or sometimes in small clusters. They are most commonly found on the nose. Milia usually develop spontaneously and are commonly found on the eyelids, cheeks, forehead and sometimes the groin. 

Multiple eruptive milia, another subtype of primary milia, is widespread and will often appear abruptly over the course of several weeks up to months. Multive eruptive milia rarely occur. it is likely that multiple eruptive milia is inherited from either of the parents without any associated anomalies. 

The usual way for the physician to diagnose milia is based on clinical findings. Milia do not need any intervention apart from observation. However, incision and drainage of the keratin content making up milia will help confirm the diagnosis. Additionally, milia which are secondary to an associated condition may require investigation to determine the primary cause. This happens when the clinician also deems present other clinical findings.²

Treatment options

Treatment options for milia depend on its subtype. In the case of congenital milia, there is no requirement for any treatment options, as these milia do most of the time resolve on their own. Other forms of milia, particularly milia secondary to an associated condition, may not resolve with time and further surgical input might be necessary. Most often surgery to remove milia is done by making small incisions with a scalpel whilst applying pressure with an extractor. 

Other effective treatments for milia are electrocautery or the use of topical retinoid solutions or chemical peels.^3,4

Milia prevention

Although milia is not always preventable, such as in the case of juvenile milia or when its growth is associated with other skin conditions, there are some treatment options that can help reduce the growth of milia. 

Some ways to prevent milia are:

• Staying away from prolonged exposure to UV rays, such as the sun
•  Avoiding the use of oil-based skin products, including thick creams
• Using an exfoliating cream two to three times a week

Sometimes, milia can arise from undergoing a chemical peel. This can be prevented by the application of a topical retinoid prior to the procedure. It is also known that retinoids when used in combination with chemical peels can cause severe irritation, which is why it is best to consult a specialist prior to using these two in combination.

Finally, a useful tip for preventing milia is maintaining good skin hygiene and applying sunscreen with a high SPF.²

When to seek medical advice

Milia do not cause any problems in both short and long term. A great number of milia cases are resolved without any treatment over the course of a few weeks. Milia are not considered harmful.

The small lumps tend to disappear quicker in babies compared to children and adults.

In the event that milia do not disappear within a few weeks, or there is associated irritation or discomfort of the skin, one should check in with their physician. This is to confirm the diagnosis or milia or to suggest a different treatment.²

Summary

Milia is a benign and temporary cyst formed of keratin that appears on the skin. Milia are commonly found on the face, particularly around the nose area. Even though milia are seen in around half of the newborns, they do not raise clinical concerns.
Milia in newborn babies will resolve by one month of life, without leaving any scars, due to its self-limiting characteristic. If milia are present in older age groups, there is a possibility that this is associated with an underlying skin condition or trauma to the skin. It is important that in these mentioned age groups other etiologies should be taken into consideration by the treating physician with a potential referral to dermatology.²