Q1. What types of alopecia have been found?

A. There are four types of alopecia.

Androgenic alopecia (AGA)

People with this type of alopecia have hair that is too soft. AGA is hereditary in general. You might worry about your hair getting thin if your father also had such a hair problem. Steroidal testosterone, most of which is made in the testis, combined with a kind of enzyme called 5 – α reductase in the roots of hair, results in powerful testosterone, namely, dihydrotesosterone (DHT). DHT is thought to cause AGA. When DHT, combined with proteins that function as a receptor of DHT, operates on sebaceous glands on the scalp, excessive sebum is secreted, which prevents hair growth. This shortens the cycle of hair growth, and thus, new hair remains fluffy, stops growing, and finally falls out. Because proteins that work as DHT receptors gather in the frontal region and top of head in particular, hairs on these regions are the most likely to fall out.

Alopecia pityroides

This type of alopecia is due to excessive dandruff. Everyone has more or less dandruff on his or her scalp, but, if he or she has scalp keratosis, excessive sebum, mixed with dandruff, this covers the pores on the scalp. This damages cells that produce new hairs, resulting in hair loss. In some cases, this type of alopecia leads to loss of hairs on only some regions of the head, but in others, it causes hair loss all over the head.

Seborrheic alopecia

This type of alopecia is due to excessive sebum and/or oily dandruff, which cover the roots of the hair. Oxidized sebum damages cells that produce new hair. It also makes it difficult for hair to “stick to”the scalp, resulting in hair loss. Sebaceous secretion is related to life styles, eating habits, and individual constitution.

Alopecia areata

　This type of alopecia is characterized by one or several bald spots that vary in size from a grain of rice to a quarter coin. These bald spots sometimes grow together, and in the worst case, hair all over the head falls out. The reason for this type of alopecia is because too much stress prevents blood flow and nerve functions, which, in turn, hinders cells from producing new hair. This alopecia is also due to excessively sensitive physiological responses.


Back