Hair Thinning Is More Common Than You Think

Noticing more hair in the shower drain or a widening parting in the mirror can be alarming. But hair thinning is extremely common — it affects people of all genders, ages, and ethnicities. The key to addressing it effectively is identifying the underlying cause, because different types of hair loss require different approaches.

1. Androgenetic Alopecia (Hereditary Hair Loss)

This is the most common cause of hair thinning globally. In men, it typically presents as a receding hairline or thinning crown. In women, it more often appears as a widening of the central parting or general diffuse thinning.

The process involves dihydrotestosterone (DHT), a hormone derived from testosterone. DHT binds to receptors in genetically susceptible follicles and causes them to miniaturise — the hair produced becomes progressively finer and shorter until the follicle stops producing hair entirely.

What helps: Ingredients that block DHT production (such as saw palmetto or finasteride in prescription form), or that counteract its effects at the follicle level (such as minoxidil).

2. Telogen Effluvium (Stress-Related Shedding)

Telogen effluvium occurs when a physical or emotional stressor pushes a large number of hair follicles simultaneously into the resting (telogen) phase, resulting in noticeable shedding 2–3 months after the triggering event. Common triggers include:

  • Major illness, surgery, or high fever
  • Significant emotional stress or trauma
  • Crash dieting or sudden dramatic weight loss
  • Childbirth (post-partum hair loss)
  • Starting or stopping certain medications

What helps: In most cases, telogen effluvium resolves on its own once the trigger is removed and stress is managed. Scalp tonics and nutritional support can assist recovery.

3. Nutritional Deficiencies

Hair follicles are among the most metabolically active structures in the body and are therefore sensitive to nutritional shortfalls. Key nutrients linked to hair thinning include:

  • Iron: Low ferritin (stored iron) is closely associated with hair loss, particularly in women.
  • Zinc: Essential for follicle cell division and protein synthesis.
  • Vitamin D: Receptors in the follicle are thought to play a role in the hair cycle.
  • Biotin (B7): A deficiency can cause hair loss, though deficiency is relatively rare in those eating a balanced diet.
  • Protein: Hair is made of keratin, a protein. Inadequate protein intake can lead to weaker, slower-growing hair.

4. Scalp Conditions

An unhealthy scalp environment can directly impair follicle function. Conditions to be aware of include:

  • Seborrheic dermatitis: Chronic inflammation of the scalp that can, over time, affect follicle health.
  • Scalp psoriasis: Thickened, scaly plaques that can block follicles.
  • Excess sebum buildup: Clogs follicle openings and creates an environment that may accelerate the bad hair cycle (悪循環).

5. The "Bad Hair Cycle" (悪循環 — Akujunkan)

Japanese hair care philosophy often highlights the concept of akujunkan — a negative feedback loop where poor scalp health leads to weaker hair, which leads to more shedding, which further compromises the scalp. This cycle can be triggered by a combination of stress, poor diet, incorrect hair care habits, and environmental factors working together.

6. Hormonal Changes

Beyond DHT, other hormonal shifts can affect hair density. These include thyroid dysfunction (both hypo- and hyperthyroidism), changes in oestrogen and progesterone (as seen during menopause or after stopping hormonal contraception), and elevated cortisol from chronic stress.

The Takeaway: Know Your Type

Hair thinning is rarely caused by a single factor. If you're experiencing noticeable hair loss, consider visiting a dermatologist or trichologist who can assess your specific pattern and order relevant blood tests. Once the cause (or combination of causes) is identified, you can build a targeted treatment plan — rather than guessing which product to try next.