• Alopecia areata. This hair loss disorder is characterized by sudden loss of hair, most commonly in small patches. The hair grows back after several months. However, if all body hair is suddenly lost, regrowth may not happen. The exact cause of this type of hair loss is unknown. Researchers believe that this type of hair loss is due to an autoimmune condition. Alopecia areata is usually seen as small areas of hair loss. If hair loss is complete on the scalp, it is called alopecia totalis. If all body hair is lost, it's called alopecia universalis.
• Toxic alopecia.Toxic alopecia may happen after a high fever or severe illness. Certain medicines, especially thallium, high doses of vitamin A, retinoids, and cancer medicines may also cause it. Medical conditions, such as thyroid disease, and giving birth may also trigger toxic alopecia. The condition is marked by temporary hair loss.
• Trichotillomania (hair pulling). Hair pulling may cause hair loss. This condition is common in young children.
• Scarring or cicatricial alopecia. Scarred areas may prevent the hair from growing back. Scarring may happen from burns, injury, or X-ray therapy. However, other types of scarring that may cause hair loss can be caused by diseases. These include lupus, bacterial or fungal skin infections, lichen planus, sarcoidosis, tuberculosis, or skin cancer.

The interest in hair replacement has gone up over the past several years. There are a number of hair replacement techniques available. But, hair replacement surgery can’t help those with total baldness. Candidates for hair replacement must have a healthy growth of hair at the back and sides of the head. The hair on the back and sides of the head will serve as hair donor areas where grafts and flaps will be taken.

There are 4 primary different types of hair replacement methods, including the following:

• Hair transplant. During a hair transplant, the surgeon removes small pieces of hair-bearing scalp from the back or sides of the head to be used as grafts. These grafts are then relocated to a bald or thinning area.
• Scalp expansion.In this procedure, a device called a tissue expander is placed underneath a hair-bearing area that is located next to a bald area. After several weeks, the tissue expander causes the skin to grow new skin cells. Another operation is then needed to place the newly expanded skin over the adjacent bald spot.
• Flap surgery. Flap surgery is ideal for covering large balding areas. During this procedure a portion of the bald area is removed and a flap of the hair-bearing skin is placed on to the bald area while still attached at one end to its original blood supply.
• Scalp reduction. Scalp reduction is done to cover the bald areas at the top and back of the head. It involves first removing the bald scalp. Then sections of the hair-bearing scalp are pulled together filling in the bald area. This can be done alone or with hair transplantation.