What causes alopecia

Overview

Alopecia is the medical term for hair loss. It can affect the scalp or the entire body, and it can be temporary or permanent. While hair loss is a natural part of aging for many, it can also be a sign of underlying health issues or a source of significant distress for individuals experiencing it.

Common Causes of Alopecia

Androgenetic Alopecia (Hereditary Hair Loss)

This is the most common cause of hair loss worldwide, affecting millions of people. It's often referred to as male-pattern baldness or female-pattern baldness. Androgenetic alopecia is driven by a combination of genetics and hormones. Specifically, it involves a sensitivity of hair follicles to a hormone called dihydrotestosterone (DHT), a byproduct of testosterone. In genetically susceptible individuals, DHT shrinks hair follicles, leading to shorter, finer hairs and eventually stopping hair growth altogether. The pattern of hair loss differs between men and women: men typically experience a receding hairline and thinning at the crown, while women usually have diffuse thinning over the top of the scalp, with the frontal hairline often remaining intact.

Alopecia Areata

Alopecia areata is an autoimmune disorder. In this condition, the body's immune system mistakenly attacks its own hair follicles, causing hair to fall out in patches. The affected areas are often smooth and round. While it most commonly affects the scalp, it can also cause hair loss in other parts of the body, including eyebrows, eyelashes, and beard. In some cases, it can progress to alopecia totalis (loss of all scalp hair) or alopecia universalis (loss of all body hair). The exact trigger for alopecia areata is unknown, but genetics and environmental factors are thought to play a role.

Telogen Effluvium

Telogen effluvium is a type of temporary hair loss that occurs when a significant stressor causes a large number of hair follicles to enter the resting (telogen) phase prematurely. Normally, about 10-15% of hairs are in the telogen phase, but with telogen effluvium, this number can jump to 30% or more. This is usually triggered by a major physical or emotional shock, such as surgery, severe illness, childbirth, significant weight loss, or extreme psychological stress. The hair loss typically becomes noticeable a few months after the triggering event and usually resolves on its own once the stressor is removed.

Medical Conditions and Treatments

Several medical conditions can lead to hair loss. Thyroid problems, both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid), can disrupt the hair growth cycle. Nutritional deficiencies, particularly iron deficiency (anemia) and deficiencies in vitamins like B12 and D, can also contribute to hair thinning. Scalp infections, such as ringworm (tinea capitis), can cause patchy hair loss and inflammation. Autoimmune diseases other than alopecia areata, like lupus, can also result in hair loss. Furthermore, certain medical treatments are notorious for causing hair loss. Chemotherapy drugs, designed to kill rapidly dividing cancer cells, also affect healthy hair follicle cells, leading to significant hair loss (anagen effluvium). Radiation therapy to the head can also cause permanent hair loss in the treated area.

Hormonal Changes

Fluctuations in hormone levels can significantly impact hair growth. Pregnancy is a common example; many women experience thicker, fuller hair during pregnancy due to increased estrogen levels, which prolong the growth phase of hair. However, after childbirth, hormone levels return to normal, often leading to postpartum hair loss (a form of telogen effluvium). Menopause is another period of hormonal change that can lead to hair thinning in women as estrogen levels decline.

Medications

A wide range of medications can cause hair loss as a side effect. These include drugs used to treat high blood pressure (like beta-blockers and ACE inhibitors), arthritis, depression, heart problems, and gout. Blood thinners (anticoagulants) and high doses of vitamin A can also contribute. It's important to consult with a doctor if you suspect a medication is causing your hair loss, as they may be able to adjust the dosage or switch to an alternative.

Physical and Emotional Stress

As mentioned with telogen effluvium, significant physical or emotional stress can disrupt the hair growth cycle. This can include anything from a high fever, severe infection, or major surgery to the death of a loved one or even intense emotional turmoil. The body diverts resources away from non-essential functions like hair growth during times of stress.

Hair Care Practices and Styling

While less common as a primary cause of widespread alopecia, certain harsh hair styling practices can lead to hair loss. Traction alopecia occurs when hair is consistently pulled too tight, such as in tight braids, ponytails, or extensions. Chemical treatments like perms, relaxers, and dyes, if used excessively or improperly, can damage the hair shaft and even the follicle. Over-brushing or aggressive towel-drying can also contribute to breakage and thinning over time.

When to See a Doctor

If you are experiencing sudden or patchy hair loss, or if your hair loss is causing you significant distress, it is advisable to consult a healthcare professional. A doctor can help diagnose the underlying cause of your alopecia through a physical examination, medical history review, and potentially blood tests or a scalp biopsy. Early diagnosis and treatment can often help manage or reverse hair loss, especially if it is related to an underlying medical condition or a medication side effect.