Alopecia areata is a disease of the hair follicles. In simple terms alopecia areata is a condition of hair loss. It is a disease characterized by hair loss which occurs in bald patches on the scalp. In most cases, hair falls out in small, round patches about the size of a coin. When there is total hair loss on the scalp then the condition is known as alopecia totalis. In cases when there is complete loss of body hair, the condition is known as alopecia universalis.
Normal Hair Cycle
The normal hair growth cycle consists of two phases which are mentioned as below:
1. Phase one of hair cycle is known as anagen phase
Hair follicles are a part of the skin from which the hair grows. Normally each hair follicle on the scalp produces a number of hairs throughout the life of the individual. Hair grows from the base of the hair follicle. The rate at which the hair grows is about 1cm a month. This hair growth usually lasts for about three years. This growth phase in the hair cycle is called anagen.
2. Phase two of hair cycle is known as telogen phase
After the growth phase or the anagen phase, the hair dies. There is no further growth of the hair. As a result of this hair lies in the hair follicle in a dormant state. The telogen phase or the dormant phase of the hair lasts for about a three month period in normal circumstances.
After the telogen phase, the hair grows again. The new growing hair pushes the old dead hair out from the hair follicle. This results in shedding of the old hair and there is hair loss. But at the same time the new hair is growing and this marks the beginning of the anagen phase. This hair cycle of shedding the old hair and growth of new hair continues throughout the life of the individual.
Alopecia areata is an autoimmune disease. In the case of alopecia areata the immune system of the body starts attacking the hair follicles in the anagen phase or the growth phase. As a result of this the telogen phase or phase in which there is shedding of the old dead hair or hair loss continues as per normal. However, since the hair follicles are attacked in their growth phase, there is no more growth of the new hair. This results in the formation of bald patches on the scalp and other parts of the body. This results in hair loss. The areas of hair loss are usually random and can involve hairs in any part of the body. The common body parts affected by this condition are eyebrows, eyelashes and the scalp.
What causes alopecia areata is still a mystery. Some scientists have linked the disease to a genetic tendency. Some scientists have identified certain trigger factors such as viral infections and stress. But the exact cause of alopecia areata is not yet known.