What causes hair loss?

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Hair Loss: Causes, Types, Symptoms, and Management

Hair loss may occur due to seasonal changes, stress, iron deficiency, and hormonal imbalances. However, prolonged or excessive hair loss can also be a sign of serious underlying diseases.

What is Hair Loss?

A healthy human scalp contains approximately 100,000 hair follicles, and shedding of about 100–150 hairs per day is considered normal in adults due to washing and combing.

Hair loss may occur due to:

  • hormonal and nutritional factors

  • exposure to chemicals

  • genetic predisposition

  • systemic diseases

  • hair growth disorders

  • medications

  • psychological stress

  • scalp diseases

In healthy individuals, hair shedding may last up to 2 months. Hair loss that occurs 3 times per year and lasts longer than 2 months may indicate an underlying medical condition and requires specialist evaluation.

Hair shedding usually begins 3–4 months after a triggering event and may return to normal 6–12 months after the cause is treated.

Each hair follicle follows a life cycle consisting of growth, rest, and shedding phases. Hair grows approximately 1 cm per month during the growth phase. After this phase, it enters a short resting period lasting a few weeks, followed by the shedding phase, which lasts 2–4 months. During this period, hair detaches from the follicle and falls out naturally.

At any given time:

  • 85–90% of hair is in the growth phase

  • 1–2% is in the resting phase

  • 10–15% is in the shedding phase

This explains why losing up to 100 hairs per day is considered normal.

Causes of Hair Loss

Each hair has a natural life cycle of 4–6 years, after which it sheds and is replaced by new hair. Hair loss becomes a concern when shedding exceeds normal limits.

Genetic factors

Male and female pattern hair loss (androgenetic alopecia) is genetically influenced. It affects over 50% of men and 20–25% of women. It is a chronic condition that may progress over time. Early treatment, including mesotherapy and PRP, can slow progression.

Skin diseases

Scalp conditions such as:

  • psoriasis

  • eczema

  • acne

  • lichen diseases

  • fungal infections

  • excessively oily skin

may lead to hair loss. Treating the underlying skin condition is essential.

Poor nutrition

Irregular eating habits, long-term fasting, single-type diets, and high-carbohydrate diets can contribute to hair loss. A balanced diet is essential for treatment.

Vitamin and mineral deficiencies

Deficiencies in:

  • vitamin B12

  • vitamin D

  • folic acid

  • biotin

  • zinc

  • iron

may lead to hair shedding. Even without anemia, low iron stores can contribute to hair loss.

Hormonal disorders

Irregular menstruation, acne, weight gain, or increased hair growth alongside hair loss may indicate hormonal imbalance. Diagnosis requires blood tests performed under specialist supervision.

Internal diseases and medications

Conditions such as:

  • thyroid disorders

  • diabetes

  • autoimmune diseases

  • kidney or liver disease

  • insulin resistance

and medications such as hormonal drugs, antidepressants, chemotherapy agents, and oral contraceptives may cause hair loss.

Sudden hair loss may also follow:

  • surgery

  • fever

  • severe infections

  • trauma

  • drug toxicity

Postpartum and chemotherapy-related hair loss

Postpartum hair loss typically begins 2–3 months after delivery due to hormonal changes and is usually temporary. Chemotherapy-induced hair loss is also generally reversible after treatment ends.

Cosmetic and mechanical factors

Frequent heat styling, tight hairstyles, bleaching, and chemical treatments may damage hair and cause breakage and shedding.

Stress and psychological factors

Severe stress, anxiety, depression, and psychiatric medications can contribute to hair loss. Stress itself may also worsen shedding.

Other causes

  • thyroid hormone disorders

  • autoimmune reactions

  • infections from dental disease

  • chronic systemic illness

Types of Hair Loss

Male pattern hair loss

Genetic androgen-dependent hair loss affecting men and women. It causes progressive thinning, especially on the top of the scalp.

Alopecia areata

An autoimmune condition causing sudden, round, completely hairless patches. It is not contagious. It may also affect beard areas and can improve over time with treatment.

Thyroid-related hair loss

Hypothyroidism or hyperthyroidism may cause diffuse hair shedding. Hair usually begins to recover about 8 weeks after treatment.

Vitamin deficiency-related hair loss

Postpartum hormonal changes and nutrient deficiencies (iron, zinc, B12, vitamin D, folate) are common causes of diffuse hair loss.

Stress-related hair loss

Often triggered by medications or physiological stress. Persistent shedding beyond 2 months should be medically evaluated.

Dental infection-related hair loss

Chronic dental infections may trigger immune responses that can affect hair follicles and lead to shedding.

What helps reduce hair loss?

  • Avoid tight hairstyles

  • Limit heat styling tools

  • Use mild shampoos suitable for hair type

  • Maintain a balanced diet rich in omega-3, B12, folic acid, and vitamin D

  • Increase water intake

  • Scalp massage

  • Reduce stress

  • Avoid chemical treatments

  • Quit smoking

  • Use supportive treatments such as minoxidil-containing products (under medical guidance)

Healthy Hair Care Recommendations

  • Avoid extreme dieting

  • Maintain regular sleep patterns

  • Reduce stress

  • Correct vitamin and mineral deficiencies

  • Stop smoking and alcohol use

  • Consume antioxidant-rich fruits and vegetables

  • Avoid fast food

  • Ensure proper medical evaluation if shedding is excessive

When to see a doctor?

Consult a specialist if:

  • hair loss exceeds normal daily limits

  • visible thinning occurs

  • shedding persists for more than 2 months

  • scalp or systemic symptoms are present