By Dr. Nixcela Ares, Founder of Dr. NAR Beauty

Alopecia means hair loss.

Alopecia is a common clinical complaint that can result from a variety of disorders.

How many hair follicles are in the human scalp?

The human scalp contains approximately 100,000 to 150,000 hair follicles.

What are the cycles of hair growth?

Hair follicles undergo lifelong cycling characterized by periods of growth (anagen), transformation (catagen), and rest (telogen). In humans, hair cycling is not all at once meaning mass shedding of hair does not occur.

• Approximately 90% of scalp hair follicles are in the anagen phase at any given time. The rate of hair growth and the duration of anagen vary with the type of hair and location. On the scalp, the growth rate of terminal hair is approximately 0.3 mm per day and the duration of anagen ranges from two to six years. In contrast, eyebrow hair grows only at a rate of 0.1 mm per day and has an anagen phase of two to three months.
• During catagen, the lower portion of the hair follicle regresses and hair production ceases. The duration of catagen on the scalp is usually around three weeks. Less than 1 percent of follicles on the scalp are in catagen.
• The telogen phase  known as the resting phase, follows catagen and lasts for two to three months on the scalp. Normally, up to 10 percent of scalp follicles are in telogen.

Normally, between 50 and 150 telogen hairs are shed per day.

Anagen follows the telogen phase, resulting in the production of a new hair. Prolongation of the telogen phase, as in conditions like telogen effluvium, can result in a reduction in hair density due to a failure of follicles to reenter anagen after shedding.

What are the types of hair loss?

Hair loss can be: cicatricial (scarring) alopecia, non-scarring alopecia, and structural hair disorders.

Cicatricial alopecia are conditions that lead to the irreversible cessation of hair cycling and permanent hair loss.

In non-scarring alopecia, the hair follicle is not permanently damaged, making spontaneous or treatment-induced regrowth a possibility.

Structural hair disorders that lead to hair loss demonstrate abnormalities within the hair shafts that result in hair fragility.

What are the most common types of non-scarring alopecia?

• Alopecia areata – this is the most frequent and hair loss occurs in patches.
• Pressure-induced (postoperative) alopecia – this is a transient hair loss caused by pressure induced on the scalp. It can occur some weeks after a long operative procedure where general anesthesia was used. In most patients, the hair regrows.
• Traction alopecia – this results from prolonged pull or tension on the hair follicle, as in tight ponytails. Longstanding traction may cause a permanent hair loss.
• Androgenic alopecia: this can occur in females or males, and is characterized by the slow, progressive loss of hair in a characteristic distribution. 
• Trichotillomania – this is a psychiatric disorder in which individuals repeatedly pluck hairs from the scalp or other hair-bearing areas.
• Anagen effluvium – this result from an acute interruption of the anagen phase and leads to extensive hair loss. Hair loss occurs within two weeks of an inciting event. Chemotherapy is one of the most common causes.
• Telogen effluvium – this is due to a major physical or psychologic stressors, childbirth, dietary restriction, and medications. Hair loss usually occurs two to three months after the inciting event.

Non-scarring alopecia may also occur with acute or chronic inflammatory skin diseases like psoriasis, atopic dermatitis, seborrheic dermatitis, and contact dermatitis, that affect the scalp and can result in focal or diffuse hair loss.

Patients with systemic lupus erythematosus may develop “lupus hair” (dry, coarse hair along the frontal hair line that usually occurs in association with disease flares). Patients with systemic lupus erythematosus may also develop telogen effluvium because of disease exacerbations or medical treatments.

Is there any treatment for non-scarring alopecia? 

Alopecia areata can be treated with systemic, topical, or intralesional steroid and/or immunotherapy.

Androgenic alopecia can be treated with antiandrogenic therapy, light laser therapy, or hair transplantation.

Vitamin D helps regrow hair by stimulating new and old hair follicles.

Is there any treatment for scarring alopecia?

In scarring alopecia the hair follicles are destroyed and replaced with scar tissue. The hair loss in scarring alopecia is permanent and cannot be reversed once scarred.