Hair loss in patches can be due to number of conditions. Most common is alopecia areata followed by tine capitis, traction alopecia and trichotillomania. Rarer causes are ringworm and syphilis or one of the patchy forms of scarring hair loss.
The sudden appearance of bald patches. When not treated these patches extend and then usually stop and recover. Most commonly this happens after only a small percentage of scalp is affected. Sometimes larger areas greater than 50% of the scalp are affected. Rarely all the hair on the head falls out (alopecia totalis) and even more rarely all body hair is lost (alopecia universalis).
On examination under a dermatoscope dormant follicles are visible which is different from the scarring alopecias where no empty follicles are seen. Also present are exclamation hairs where the hair is thinner at the base than at the broken top.
AA can sometimes be confused with the fungal infection tinea capitis, traction alopecia from hair pulling or trichotillomania (obsessive compulsive hair pulling).
CAUSE Alopecia areata is caused by the body’s immune system attacking the hair follicle. No one knows why it affects some and not others but it is exacerbated by stress and tends to run in families. It can be related to an underactive thyroid. The natural history of untreated alopecia areata varies. Some people only get one or two small patches which are easily camouflaged or disguised until full recovery occurs. New hair may be white or grey at first but usually returns to it’s normal colour.
Those with more extensive loss take longer to recover and those with alopecia totalis or universalis may never recover. Alopecia areata tends to be more severe, more prolonged, harder to treat and more likely to recur when:
- more than 50% of the scalp is affected
- when it develops under the age of 10 years
- in those with eczema.
TREATMENT Treatment may not be needed. Treatment is directed towards triggering recovery. Once recovery is initiated it tends to continue on it’s own and treatment can stop. When treatment is needed options are:
- steroid cream
- steroid injections
- topical minoxidil lotion
- dithranol cream
- essential oils
- platelet rich plasma
- skin needling
- liquid nitrogen
- topical immunotherapy for severe cases
- in 2014 a class of drugs known as JAK inhibitors have been found to reverse alopecia totals.
Fungal infection of the scalp. This form of hair loss is usually accompanied by itch, sometimes scale (dandruff) and occasionally crusts. It may be patchy but diffuse tines capitis is not uncommon in adults with hair loss.
As well as the clinical features mentioned above there may be comma shaped or corkscrew shaped hairs lost by shedding or visible under a dermatoscope. Some fungi may glow under a Woods Light but not all of them do.
CAUSE In children it is most commonly caused by either the Microsporum fungus passed on by animals, usually kittens. In adults it is most commonly caused by the human fungus Trichophyton. These are different to the Malassezia fungi that cause seborrhoeic dermatitis (dandruff).
TREATMENT is anti fungal shampoo (e.g. ketoconazole) and antifungal tablets, most typically itraconazole.
Uncontrolled picking and pulling of hair due to stress, anxiety or OCD. Leads to sparse and plucked areas. This is the most serious psychological cause of hair loss. It is usually managed with counselling and antidepressants but may respond to the supplement N acetyl cysteine. Older children with trichotillomania often adamantly deny that they are pulling out their hair.
Hair loss due to hair clips, rollers, cornrows or dreadlocks. The only cure is to remove the cause and, even then, the scalp may not fully recover. The scarring forms of hair loss lichen planopilaris and pseudopelade will also usually present with patchy hair loss.