- Hair consists of two parts: the follicle within the skin and the shaft (which we see outside the scalp). Hair shaft that is visible is dead, and is made up of keratin. On an average, a person has approximately 100000 strands of hair on the head that grow by 0.3-0.4 mm/day and up to 6 inches in a year.
- A unique feature of hair is that it goes through a growth and rest phase. A follicle that disintegrates completely in the terminal phase, is replaced by a new follicle in the growth phase.
- Unlike in other mammals, human hair does not follow a cycle of shedding; however, there is a random pattern of hair shedding that sets different stages of hair growth.
- The hair growth consists of 3 stages: Anagen is the first phase and an active phase with the growth of new hair; in this phase the hair grows by 1cm every 28 days. Catagen is the second phase of growth, and 3% of the hair is in this phase at all times. Telogen is the resting phase; during this phase 25-100 telogen hairs are shed daily, which is normal.
- At any time on a healthy human scalp, 80 to 90% of the hair is in the active phase of growth. Scalp hair remain in the anagen phase for 2 to 6 years, while hair on the other parts of the body has a shorter anagen phase of 30 to 45 days, hence the shorter size.
- The hair density is the total number of hair follicles per square centimeter of the scalp. As we grow older the density of hair decreases; this is because of the expansion of scalp as we grow.
- Alopecia refers plainly to hair loss. It is not a specific clinical diagnosis. The most common type of hair loss that is seen is androgenetic alopecia. In early stages of androgenetic alopecia, up to 40% of the hair follicles may remain in the resting phase (telogen).
- Telogen effluvium is the second most common type of hair loss. It is caused due to a change in the number of hair follicles. This is a temporary condition, where more follicles are in resting phase than required, and this can occur due to stressful conditions (like accidents), change in hormones, dietary factors, intake of certain medication (like antidepressants) and chronic diseases.
- Patchy baldness on the scalp can occur as a result of autoimmune conditions in men and women of any age group (especially teenage and younger adults). The immune system attacks the hair follicle assuming it to be a foreign body thus resulting in hair loss. This condition is called alopecia areata and is seen in only 2 of 100 people. If seen in children it may persist in adulthood.
- Ringworm infection is a fungal infection of the scalp that can cause scaling and temporary hair loss. It is infectious and spreads by direct contact with an infected person. Some infections may resolve spontaneously, but in some cases antifungal medication like griseofulvin is required.
- Seborrheic dermatitis is an inflammatory condition of the skin that can result in temporary loss of hair when the scalp is affected. This condition is linked to stress, chronic fatigue, head injury and diseases like Parkinson#$#s. It presents with an oily, itchy and painful scalp and also produces an environment conducive for infection.
- If hair loss is found around the beard area, then it is called alopecia barbae. Hair loss that covers the entire scalp is called alopecia totalis. If it involves the whole body including the eyebrows, beard, eye lashes, and pubic hair, it is called alopecia universalis.
- The binding of dihydrotestosterone or DHT (formed by the conversion of testosterone, male hormone) to receptors in hair follicles is linked with hair loss. DHT causes shrinking of the follicles, and hence makes it difficult for healthy hair to survive.
- Surgical hair treatment requires harvesting hair from the scalp of the patient, usually the sides and back of scalp where it is less affected by dihydrotestosterone (DHT) and then transplanting it into areas of baldness. Hair cannot be harvested from another person and used for transplant as the recipient body will reject it.
- Non-surgical hair replacement is a solution for people with severe hair loss. This consists of a hair piece which has a base made of mesh or polythene into which the hair is tied or injected. However, the lack of quality and proper selection can result in lack of compliance to this hair prosthesis. In America, 70% customers were unhappy with the product.
- Hair loss Facts - (http://www.hightechscience.org/funfacts.htm)
- Introduction to Hair Loss - http://americanhairloss.org/hair_loss_research/introduction.asp)