Hair Loss Explained

What Is Hair Loss?

Hair grows everywhere on the human body except on the palms of the hands and the soles of the feet, but many hairs are so fine they' are invisible. Hair is made up of a protein called keratin (the same protein in nails) produced in the 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 six inches a year. The hair you can see is a string of dead keratin cells. The average adult head has about 100,000 to 150,000 hairs and loses up to 100 of them a day; so finding a few stray hairs on your hairbrush or here and there is not necessarily  anything to be concerned about.

At any one time, 90% of the hair on a person's scalp is growing. Each follicle has its own life cycle and can be influenced by age, disease, and a wide variety of other factors. This life cycle of the follicle is divided into three phases:

Anagen -- active hair growth. Which lasts between two to six years.
Catagen -- transitional. Which lasts two to three weeks.
Telogen -- resting phase. At the end of the resting phase (two to three months) the hair is shed and a new hair replaces it and the growing cycle begins again.
As people age, their rate of hair growth slows.

There are many types of hair loss, which is also called alopecia:

Gradual thinning of the hair with age is a natural condition known as involutional alopecia. And more and more hair follicles go into a telogen, or resting, phase, and the remaining hairs become shorter and fewer in number.

Androgenic alopecia is another form of hair loss. It is a genetically predisposed condition that can affect both men and women. Most men with this condition can begin suffering hair loss as early as their teens or early 20s, while most women don't experience noticeable thinning until their 40s or later.

In men, this condition is also called male pattern baldness. It's characterized by a receding hairline and gradual disappearance of hair from the crown. And in women, androgenic alopecia is referred to as female pattern baldness. Women with this condition experience a general thinning over the entire scalp, with the most extensive hair loss at the crown.

Patchy hair loss in children and teens or young adults, often sudden in onset, is known as alopecia areata. This condition may result in complete baldness, but in about 90% of cases the hair returns, usually within just a few years.

With alopecia universalis, all the body hair falls out.

The tearing out one's own hair, a psychological disorder known as trichotillomania, is seen most frequently in children.

Telogen effluvium is hair thinning over the scalp or other parts of the body that occurs because of changes in the growth cycle of the hair. A large number of hairs do enter the resting phase at the same time, causing shedding and subsequent thinning.

What Causes This Hair Loss?

Doctors don't know why certain hair follicles are programmed to have a shorter growth period than others. Although a person's level of androgens -- male hormones that are normally produced by both men and women -- is believed to be a factor, hair loss has nothing to do with virility. The presence or absence of dandruff has no effect on balding either. An individual's genes, however -- from both male and female parents -- do influence that person's predisposition to male or female pattern baldness.

Telogen effluvium is the term for temporary hair loss that can occur within a few months after a high fever, a severe illness, thyroid diseases, iron deficiency, medications, hormonal imbalance, or extreme stress, and in women following childbirth.

The drugs that can cause temporary hair loss include chemotherapeutic agents used in cancer treatment, anticoagulants, retinoids used to treat acne and skin problems, beta-adrenergic blockers used to control blood pressure, and oral contraceptives.

Hair loss can also be caused by burns, X-rays, scalp injuries and ringworm.

The causes of alopecia areata, a disease that often strikes children or teenagers, still remain unexplained. It's thought to be an autoimmune disease, meaning that the immune system revs up for unknown reasons and then destroys the hair follicles. In most cases the hair grows back, although it may be very fine and possibly of a different color before normal coloration and thickness return.

Although too-frequent washing, permanent waves, bleaching, and dyeing the hair do not cause baldness, they can contribute to overall thinning by making hair weak and brittle. Tight braiding and using rollers or hot curlers can damage and break hair, and it's not well known but running hair picks through tight curls can scar hair follicles. In most instances hair does grows back normally if the source of stress is removed, but severe damage to the hair or scalp sometimes causes permanent bald patches.

I hope this answers any questions you may have about hair loss basics. Hair loss explained isn't always easy to understand but we have attempted to put it in simple language here.