Demodex folliculorum is a microscopic mite that commonly inhabits the hair follicles and sebaceous glands of human skin. These mites are a natural part of the skin’s microbiome and are often present without causing any noticeable issues. However, in some individuals, an overpopulation of these mites can lead to a range of skin symptoms. Nearly all adults may host small populations of these mites.
Common Signs and Symptoms
One common symptom is itching, which may be particularly noticeable at night. This itching can be accompanied by redness of the skin. The skin may also develop a rough or scaly texture. This rough sensation can occur due to an increase in skin cells within the hair follicles when mites are present in large numbers.
Additionally, individuals might experience increased skin sensitivity and a burning sensation. Some people report a feeling of something crawling on their skin. The skin may also exhibit eczema-like patches or develop pustules that resemble whiteheads. These symptoms, when grouped together, can indicate a condition known as demodicosis.
How Symptoms Appear on Different Body Areas
On the Face
On the face, symptoms often mimic rosacea, presenting as persistent redness, flushing, and the appearance of small bumps or pustules. The skin may also feel sensitive or have a gritty texture.
Around the Eyes
When mites affect the eyes, they can contribute to blepharitis, an inflammation of the eyelids. This condition can lead to symptoms such as itching, burning, and the formation of crusts along the lash line. Individuals may also experience a gritty or foreign body sensation in their eyes, and in some cases, loss of eyelashes or recurrent styes and chalazia can occur.
On the Scalp
While less common than facial or ocular symptoms, Demodex folliculorum can also affect the scalp. Here, symptoms may include itching and irritation. In some instances, an overpopulation of these mites on the scalp could be associated with hair thinning, though this connection is not as frequently observed or established as their role in facial and eye conditions.
Factors Influencing Symptom Severity
Several factors can contribute to an increased population of Demodex folliculorum mites and, consequently, more pronounced symptoms. A compromised immune system, due to conditions like HIV or the use of certain medications such as corticosteroids, can allow mite populations to grow unchecked. This imbalance can lead to more noticeable skin irritation.
Certain pre-existing skin conditions, particularly rosacea, are strongly linked to higher densities of Demodex mites. Individuals with rosacea may have significantly more mites on their skin compared to those without the condition, potentially exacerbating their symptoms. Age also plays a role, with older adults generally having a higher likelihood of mite overgrowth and related symptoms.
The skin’s microenvironment, including factors like sebaceous gland function and skin surface lipid composition, can influence mite proliferation. Although not fully understood, some research suggests that certain cosmetics or medications that alter the skin’s natural balance could also contribute to an environment favorable for mite overgrowth, leading to more severe symptomatic presentations.