Alopecia Types, Reasons, and Relations to Demodex Mites

Alopecia is a condition in which the affected person loses all or part of their hair on the head, face, or body. The issue is also known as baldness and can occur for a variety of reasons, including:

• Stress
• Childbirth
• Iron-deficiency 
• Radiotherapy
• Hormonal disorders
• Lifestyle changes
• Some medications
• Restrictive dieting

The following article will examine the types of alopecia and the role Demodex mites play in triggering and exacerbating it.

Types of Alopecia

There are different types of alopecia classified based on criteria such as the areas involved, causes, the growth stage of the hair cycle, and other characteristics. Here, we introduce some common types of hair loss:

Anagen Effluvium

This is a rapidly occurring hair loss, which is usually the result of medical procedures such as chemotherapy. This hair shedding arises by the cessation of the hair production cycle at the anagen stage of growth. It usually starts 7 to 15 days after the start of chemotherapy and leads to complete baldness in two months. Anagen Effluvium can affect all parts of the body but is usually confined to the scalp. However, hair usually grows back on its own after chemotherapy ends.

In addition to chemotherapy, we should note that any factor that affects hair strands during the growth phase, including protein malnutrition, radiation therapy, and intoxications with mercury, thallium, colchicine, can lead to Anagen Effluvium. 

Telogen Effluvium

This type of hair loss usually occurs a few months after stress or physical/psychological trauma. In this scenario, hair enters the resting phase (Telogen) without maturing, which leads to increased hair loss in the next two to three months. The hair growth phase (Anagen) may also be prolonged, resulting in telogen hair falling out without replacement. Lost hair usually grows back after six months. However, sometimes dermatologists prescribe medications to speed up the regrowth process.

In some people, due to idiopathic reasons, Telogen Effluvium lasts for more than six months but usually does not lead to complete baldness. Some of the reasons for this type of hair loss are as follows:

• Drugs: oral contraceptive pills, androgens, retinoids, beta-blockers, ACE (angiotensin-converting enzyme) inhibitors, anticonvulsants, antidepressants, and anticoagulants (heparin)
• Physiological stress: surgical trauma, high fever, chronic systemic illness, Childbirth, and hemorrhage
• Emotional Stress
• Medical Conditions: Both hyper- and hypothyroidism, systemic amyloidosis, hepatic failure, chronic renal failure, inflammatory bowel disease, and lymphoproliferative disorders, dermatomyositis, HIV, syphilis, psoriasis, and seborrheic dermatitis can also lead to diffuse telogen hair loss.
• Dietary Triggers: Severe protein, fatty acid, and zinc deficiency, chronic starvation, and caloric restriction. Decreased body iron stores, Vitamin D, and biotin deficiency.
• Ultraviolet Light: Excessive UV rays in the summer can lead to hair loss in the fall. 

Androgenic Hair Loss

Male hormones are the primary reason for hereditary or androgenic hair loss. This type of alopecia leads to complete baldness in many men. However, the hairline usually doesn't recede in women, but the strands fall out and become thinner.

Hereditary hair loss has a well-known pattern. It usually starts from the temples; the hairline gradually recedes, which eventually leaves a hair ring along the scalp's bottom.

Alopecia Areata

It is an autoimmune complication that affects the hair of the scalp and sometimes other parts like the eyebrows and eyelashes. In this complication, the immune system mistakenly assumes that the hair follicles are foreigners and attacks them. Hair usually falls out regionally in patches. Alopecia Areata can lead to alopecia totalis, in which all scalp hair falls out. Alopecia Areata can affect people of all ages.

In addition to the varieties described, there are other types of hair loss that we will only mention their names here:

• Tinea Capitis (scalp ringworm)
• Cicatricial Alopecia (scarring alopecia)
• Lichen Planopilaris
• Discoid Lupus Erythematosus
• Folliculitis Decalvans
• Dissecting Cellulitis of the Scalp
• Frontal Fibrosing Alopecia
• Central Centrifugal Cicatricial Alopecia

Scientific research shows that the proliferation of some skin parasites named Demodex has an active role in causing or exacerbating different kinds of alopecia. In fact, people with high concentrations of Demodex may undergo complications such as hair loss. In the following sections, we investigate the relationship between alopecia and Demodex mites.

What Is Demodex?

Demodex is a particular type of skin mite that resembles worms. It is extremely tiny, and you can see it just under the lens. Demodex comes in many forms. To date, two species have been discovered in human skin, called Demodex brevis and Demodex folliculorum. These mites find hair follicles and sebaceous glands suitable sites for feeding, reproducing, and shading from threatening agents.

Since the low density of these parasites is not accompanied by any signs or symptoms, you will notice their presence only when their population has sharply increased. In this case, you are likely to develop multiple skin and hair complications. People with a high density of Demodex usually have one or more of the following symptoms, or if they already have, their symptoms get worse:

• Acne
• Rosacea
• Blepharitis
• Hair loss
• Dandruff
• Itchy skin and so on