Normal Daily Hair Loss and Pathological Increases
A healthy person typically loses 50-100 hairs per day as part of the normal hair cycle, and this can significantly increase with conditions like telogen effluvium, alopecia areata, thyroid disorders, and during chemotherapy.
Normal Daily Hair Loss
While the provided evidence does not explicitly state the exact number of hairs lost daily in healthy individuals, the normal hair cycle involves continuous shedding and regrowth. The distinction between normal shedding and pathological hair loss becomes clinically relevant when patients present with noticeable thinning or bald patches.
Conditions That Increase Hair Loss
Alopecia Areata
- Alopecia areata causes patchy, non-scarring hair loss affecting the scalp and sometimes other hair-bearing areas, with characteristic "exclamation mark hairs" around expanding patches 1
- Approximately 20% of patients have a family history, suggesting genetic predisposition 1
- The condition affects hair follicles through T lymphocyte-mediated autoimmune mechanisms 1
- Spontaneous remission occurs in up to 80% of patients with limited patchy hair loss of short duration (< 1 year), though prognosis worsens with extensive involvement 1
- Patients with less than 25% hair loss initially have 68% disease-free status at follow-up, while those with more than 50% hair loss initially have only 8% disease-free status 2
- Nails are involved in approximately 10% of cases 1, 2
Thyroid Disorders
- Hypothyroidism is a well-recognized cause of diffuse hair loss and should be screened in patients presenting with alopecia 3, 4
- Thyroid autoimmunity shows strong association with alopecia areata, with subclinical hypothyroidism detected in 16% of alopecia areata patients 3
- Every patient with alopecia areata should be screened for thyroid function and thyroid autoantibodies (anti-thyroglobulin and anti-thyroid peroxidase antibodies) even without clinical manifestations 3
- Zinc deficiency can complicate hypothyroidism, as thyroid hormones are essential for zinc absorption, creating a bidirectional relationship 4
- Hair loss from hypothyroidism may not improve with thyroxine alone unless zinc supplements are added 4
Chemotherapy-Induced Alopecia
- Chemotherapy-induced alopecia occurs in approximately 48% of chemotherapy treatments with severity grade 2 (more than 50% hair loss) 5
- Hair loss typically begins 1-3 weeks after therapy initiation 5
- Affects the entire scalp and sometimes eyebrows, eyelashes, and body hair 5
Telogen Effluvium
- Telogen effluvium represents a distinct differential diagnosis from alopecia areata and causes diffuse hair shedding 1
- A common pitfall is misdiagnosing diffuse alopecia areata as telogen effluvium 2
Clinical Assessment Approach
History Taking
- Document onset, duration, and progression of hair loss 2
- Obtain family history (present in 20% of alopecia areata cases) 2
- Inquire about hair care practices causing traction alopecia 2
- Assess psychological impact, as hair loss causes significant distress 2
Physical Examination
- Examine scalp for redness, inflammation, or scaling suggesting tinea capitis 2
- Look for patchy loss with "exclamation mark hairs" indicating alopecia areata 2
- Check for broken hairs with irregular length suggesting trichotillomania 2
- Examine nails (involved in 10% of alopecia areata) 2
- Check for lymphadenopathy 2
Common Diagnostic Pitfalls
- Overlooking tinea capitis with subtle inflammation 2
- Failing to recognize trichotillomania (broken hairs remain firmly anchored, unlike exclamation mark hairs) 2
- Ordering unnecessary laboratory testing for typical pattern hair loss 2
Laboratory Workup for Suspected Pathological Hair Loss
When clinical assessment suggests pathological hair loss beyond normal shedding: