Hair on the scalp grows at a rate of about 1cm a month and each individual hair continues to grow for up to about six years.
A loss of at least 50-100 hairs a day is normal. 'Physiological' hair loss may follow the male (gradually receding hair line) or female pattern (general thinning) and is typically genetic.
Localised hair loss (alopecia areata) is likely to be autoimmune, although local fungal infection or ringworm should be ruled out.
|Red flag symptoms|
Look out for a kerion, a thickened, inflamed, pus-filled area over the scalp. This is a complication in severe tinea capitis.
Kerion is a dermatological emergency. Only prompt treatment with systemic steroids will prevent the destruction of the hair follicles and inevitable permanent hair loss.
A sudden halt in hair growth, for example through systemic cytotoxins or chemotherapy, can result in a fairly simultaneous hair loss of larger areas.
Other physical or emotional stress also can lead to a temporarily increased hair loss, which may occur with a delay of several months.
The hair lost from this 'shock-fallout' may never fully regrow.
Many medications can cause reversible hair loss: anticoagulants, hormone treatments (including contraception) antihypertensives, antidepressants, allopurinol and antirheumatics. There has been some debate as to whether male-pattern baldness may be caused by high levels of insulin.
Apart from prescribed medication consider accidental or deliberate poisoning.
Endocrine imbalances, for example of the thyroid gland (mostly in hypothyroidism), sex hormones (e.g. with polycystic ovaries) or in diabetes, can cause increased hair loss. Physiological hair loss may occur about six months after pregnancy. If the loss is significant or prolonged, consider hypothyroidism.
Anaemia or excessive weight loss can be relevant if there is a lack of iron, protein, zinc, fatty acids or vitamins.
Trauma, such as burns or radiation, often leads to scarring and therefore permanent hair loss. Over-handling such as aggressive brushing, bleaching and perming as well as wearing particularly tight hairstyles is fairly common and affects the follicles. Occasionally, children or some adults pull and twist their hair as part of behaviour problems (trichotillomania).
Establish the distribution of the hair loss and assess whether there is a scarring condition. Investigate as needed, including blood tests, and consider a referral, at least for a second opinion.
Patients with a complete hair loss have a poor prognosis for ever regaining their hair.
- Dr Jacobi is a salaried GP in York.
- Tinea capitis
- Alopecia areata
- Lichen planus
- Medication side-effects
- Trauma and 'shock fallout'