Hair and Hair Loss 101
Hair loss or baldness (technically known as alopecia) is a loss of hair from the head or body. Baldness can refer to a general hair loss, or specific patterns associated such as with male pattern baldness. Extreme forms of alopecia areata are alopecia totalis, which involves the loss of all head hair, and the most extreme form, alopecia universalis, which involves the loss of all hair from the head and the body.
Hair is made up of a protein called keratin that is produced in hair follicles in the outer layer of skin. As follicles produce new hair cells, old cells are being pushed out through the surface of the skin at the rate of about 15cm a year. The hair you can see is actually a string of dead keratin cells. At any one time, about 90% of the hair on a person's scalp is growing. Each follicle has its own life cycle that can be influenced by age, disease, and a wide variety of other factors.
The Life Cycle of Hair
This life cycle is divided into three phases:
Anagen -- active hair growth that lasts between two to six years
Catagen -- transitional hair growth that lasts two to three weeks
Telogen -- resting phase that lasts about two to three months; at the end of the resting phase the hair is shed and a new hair replaces it and the growing cycle starts again.
Each cycle consists of a long growing phase (anagen), a short transitional phase (catagen) and a short resting phase (telogen). At the end of the resting phase, the hair falls out and a new hair starts growing in the follicle beginning the cycle again. Normally, about 40 (0–78 in men) hairs reach the end of their resting phase each day and fall out. When more than 100 hairs fall out per day, clinical hair loss may occur.
Do you have excessive daily hair loss?
People have between 100,000 and 150,000 hairs on their head. The number of strands normally lost in a day varies, but on average is 100. In order to maintain a normal volume, hair must be replaced at the same rate at which it is lost. The first signs of hair thinning that people will often notice are more hairs than usual left in the hairbrush after brushing or in the basin after shampooing. Styling can also reveal areas of thinning, such as a wider parting or a thinning crown.
Types of Hair Loss (Alopecia)
There are many types of hair loss, also called alopecia:
Involutional alopecia - is a natural condition in which the hair gradually thins with age. More hair follicles go into the resting phase, and the remaining hairs become shorter and fewer in number.
Androgenic alopecia - is a genetic condition that can affect both men and women. Men with this condition, called male pattern baldness, can begin suffering hair loss as early as their teens or early 20s. It's characterized by a receding hairline and gradual disappearance of hair from the crown and frontal scalp. Women with this condition, called female pattern baldness, don't experience noticeable thinning until their 40s or later.Women experience a general thinning over the entire scalp, with the most extensive hair loss at the crown.
Alopecia areata - often starts suddenly and causes patchy hair loss in children and young adults. This condition may result in complete baldness (alopecia totalis). But in about 90% of people with the condition, the hair returns within a few years.
Alopecia universalis - causes all body hair to fall out, including the eyebrows, eyelashes, and pubic hair.
Trichotillomania - seen most frequently in children, is a psychological disorder in which a person pulls out one's own hair.
Telogen effluvium - is temporary hair thinning over the scalp that occurs because of changes in the growth cycle of hair. A large number of hairs enter the resting phase at the same time, causing hair shedding and subsequent thinning.
Scarring alopecias - result in permanent loss of hair. Inflammatory skin conditions (cellulitis, folliculitis, acne), and other skin disorders (such as some forms of lupus and lichen planus) often result in scars that destroy the ability of the hair to regenerate. Hot combs and hair too tightly woven and pulled can also result in permanent hair loss.
Causes of Hair Loss (Alopecia)
Alopecia can have many causes, including fungal infection, traumatic damage, such as by compulsive pulling, as a result of radiotherapy or chemotherapy, and as a result of nutritional deficiencies such as iron, and as a result of autoimmune phenomena, including hair loss associated with systemic lupus erythematosus.
Trauma Traction alopecia is most commonly found in people with ponytails or cornrows who pull on their hair with excessive force. In addition, rigorous brushing and heat styling, rough scalp massage, Hair treatments (chemicals in relaxers, hair straighteners) can damage the cuticle, the hard outer casing of the hair. This causes individual strands to become weak and break off, reducing overall hair volume.
Stress has been shown to restrict the blood supply to capillaries, inhibiting oxygen and nutrient uptake of hair follicles and inhibiting hair growth, in an effect similar to that from having poor circulation.
Worrisome hair loss often follows childbirth without causing actual baldness. In this situation, the hair is actually thicker during pregnancy due to increased circulating oestrogens. After the baby is born, the oestrogen levels fall back to normal pre-pregnancy levels, and the additional hair foliage drops out. A similar situation occurs in women taking the fertility-stimulating drug clomiphene.