Alopecia is a generic term used for any hair loss from part of the head or body where inflammation or scarring is not present. The severity of hair loss can vary from a small area to the entire body.
However, there are many different forms of hair loss included in the term ‘alopecia’, some are and some are not.
Other common types of hair loss include: male-pattern hair loss, female-pattern hair loss, and a thinning of hair known as telogen effluvium. These are not ‘alopecia’.
The cause of male-pattern and female-pattern hair loss is a combination of genetics and male hormones, and the cause of telogen effluvium is typically a physically or psychologically stressful event.
Telogen effluvium is very common following pregnancy, or hypothyroidism, or malnutrition including iron deficiency.
Less common causes of hair loss without inflammation or scarring include the pulling out of hair (trichotillomania), certain medications including chemotherapy, and HIV/AIDS.
Causes of hair loss that occurs with scarring or inflammation include but are not limited to fungal infection, lupus erythematosus, radiation therapy, and sarcoidosis.
Alopecia areata is the most common form of alopecia, it is used to describe patches of hair missing. The cause of alopecia areata is an autoimmune issue in which hair is lost from some or all areas of the body, usually from the scalp due to the body’s failure to recognise its own body cells and subsequent destruction of its own tissue. Often it results in bald spots on the scalp.
In 1–2% of cases, the condition can spread to the entire scalp (alopecia totalis) or to the entire skin (alopecia universalis).
There are two types: (1) scarring alopecia, where there is fibrosis, inflammation, and loss of hair follicles, and (2) nonscarring alopecia, where the hair shafts are gone but the hair follicles are preserved, making this type of alopecia reversible.
Alopecia is not contagious. It is not due to nerves. This disease most often occurs in otherwise healthy people.
Traction alopecia is not an autoimmune issue, it is caused by tying hair to tightly e.g. in corn-rows, or by hair extensions / weaves. This leaves scars and the tension destroys the hair follicle so the hair doesn’t return.
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