Why does hair regrowth sometimes stop?

Why does hair regrowth sometimes stop?

Hair naturally goes through cycles of growth (anagen), transition (catagen), rest (telogen) and shedding (exogen). Under normal conditions, about 85–90% of scalp hairs are in anagen, growing about 1–1.25 cm per month. But various factors can disrupt this cycle, causing hair regrowth to slow or stop altogether. Here’s what you need to know.

1. Disruption of the Hair Cycle
   According to Paus & Cotsarelis (1999), the hair cycle is tightly regulated by signals in the follicle. When these signals are disturbed, hairs enter telogen prematurely and stop growing.

• Telogen Effluvium
  • Triggered by stress, illness, surgery, rapid weight loss or childbirth
  • Large numbers of hairs shift into the resting (telogen) phase at once
  • Results in noticeable shedding 2–3 months after the trigger
  • Regrowth often resumes once the trigger is removed, but prolonged or repeated triggers can make hair regrowth stop

• Chronic Telogen Effluvium
  • Persistent shedding for >6 months
  • Hair thins diffusely, but the scalp is not scarred
  • May reflect ongoing nutritional, hormonal or psychological stress

2. Genetic and Hormonal Factors
   Androgenetic alopecia (male or female pattern baldness) is the most common cause of progressive hair thinning.

• Role of Androgens
  • Dihydrotestosterone (DHT) binds to hair follicle receptors, shortening anagen and shrinking follicles
  • Over time, regrowth produces thinner, shorter hairs until follicles may stop producing hairs at all

• Genetic Predisposition
  • Family history increases risk
  • Women may notice widening part lines; men see receding hairlines and balding at the crown
  • Early intervention with FDA-approved treatments (e.g., minoxidil, finasteride) can prolong anagen and delay when hair regrowth stops

3. Autoimmune Attack: Alopecia Areata
   When the immune system mistakenly targets hair follicles, regrowth can halt suddenly in patches.

• What Happens
  • T-cells surround and attack follicles in anagen phase
  • Hairs fall out in round or oval patches
  • Can progress to total scalp loss (alopecia totalis) or complete body hair loss (alopecia universalis)

• Why Regrowth Stops
  • Follicles enter a state of “dormancy” under immune attack
  • Without treatment, follicles may remain inactive or miniaturize

If you notice sudden, patchy hair loss, consider doing a free, online symptom check for Alopecia Areata.

4. Nutritional Deficiencies
   Hair follicles are among the most metabolically active cells in the body. They need a steady supply of protein, vitamins and minerals.

• Common Deficiencies
  • Iron (ferritin) — low levels linked to telogen effluvium
  • Vitamin D — supports follicle cycling
  • Biotin, zinc, protein — building blocks of keratin

• How Deficiency Stops Regrowth
  • Follicles lack resources to enter or maintain anagen
  • Cycle shifts toward rest (telogen), reducing active growth

• What to Do
  • Eat a balanced diet with lean protein, leafy greens, nuts and seeds
  • Check levels with your doctor before starting supplements

5. Physical and Emotional Stress
   Severe stress—whether physical (high fever, surgery, chronic illness) or emotional—can cause hair to abruptly halt growth.

• Mechanism
  • Stress hormones (cortisol) disrupt follicle signals
  • Inflammatory mediators push hairs into telogen

• Timeline
  • Shedding appears about 2–4 months after stress
  • Recovery usually follows once stressor resolves, but chronic stress can make hair regrowth stop entirely

• Coping Strategies
  • Mind-body techniques (meditation, yoga)
  • Adequate sleep, gentle scalp massage
  • Speak with a mental health professional if stress is overwhelming

6. Medications and Medical Treatments
   Certain drugs are known to cause hair loss or halt regrowth.

• Common Culprits
  • Chemotherapy agents (cell-division inhibitors)
  • Anticoagulants (blood thinners)
  • Retinoids, some antidepressants, beta-blockers

• Reversibility
  • Shedding often peaks within months of starting the drug
  • Hair may regrow when medication is reduced or stopped, but some treatments (e.g., certain chemotherapies) can damage follicles permanently

• What You Can Do
  • Discuss alternatives or dose adjustments with your doctor
  • Use gentle, fragrance-free hair care products
  • Consider cooling caps during chemotherapy to reduce follicle exposure

7. Scarring (Cicatricial) Alopecia
   In rare cases, inflammation permanently destroys hair follicles, replaced by scar tissue.

• Causes
  • Lichen planopilaris, discoid lupus, folliculitis decalvans
  • May present with redness, itching, pustules, loss of follicular openings

• Why Regrowth Stops
  • Follicle stem cells are destroyed
  • Scar tissue cannot produce new hairs

• Management
  • Early diagnosis by a dermatologist is critical
  • Anti-inflammatory treatments (steroids, immunosuppressants) may halt progression

When to Seek Help
If you experience any of the following, talk to your doctor:

• Sudden or patchy hair loss
• Signs of scalp inflammation (redness, pain, pustules)
• Thinning that affects self-esteem or quality of life
• Any symptoms that could be life-threatening (e.g., severe fatigue, unexplained weight loss)

Remember, while some causes of hair loss are benign and reversible, others require prompt medical attention.

Speak to a doctor about anything that could be life threatening or serious.