The Hair Cycle
At any given time, the hairs on our scalp and body are constantly falling out and being replaced. Approximately 90% of the hair on the scalp is in the growth phase (anagen), while 8-10% are in the resting phase (catagen). At the end of the resting phase is the shedding phase (telogen). On average, our hair grows just over 1 cm per month. It is normal to loose about 100 hairs per day. When a hair sheds, it is replaced by a new hair from the same follicle located just below the skin surface.
Why See a Dermatologist?
Thinning of scalp hair can be due to increase hair shedding (telogen phase) or a decrease in hair growth (anagen phase), or both. People who notice they are shedding large amounts of hair after combing or brushing, or whose hair rapidly becomes thinner or falls out in patches should consult a dermatologist. The dermatologist will evaluate the problem by asking questions about diet, medications, family history, recent illness and hair care habits. Female patients will be questioned about menstrual cycle, pregnancies, and menopause. After examination of the patient’s scalp and hair, the dermatologist may examine a few hairs under the microscope. Laboratory tests are sometimes required. It is important to understand why hair is being lost and whether or not the problem will respond to medical treatment.
Causes of Hair Loss
A number of conditions and lifestyle factors can cause excessive hair loss. For example:
Hereditary Hair Loss
Androgenetic alopecia or hereditary thinning of the hair is the most common cause of hair loss. This is present to varying degrees in greater than 50% of the population. This condition can be inherited from either the mother`s, father`s or both sides of the family. Women with this trait develop thinning hair of the frontal scalp in a diffuse fashion, but do not become completely bald. Men with androgenetic alopecia typically have receding hairlines of the frontal scalp. Hereditary hair loss can begin in one`s teens, twenties, or thirties. While there is no cure, medical and surgical treatments are available that may benefit certain individuals, including:
- Minoxidil, a foam or solution applied to the scalp twice a day, which can be used by men and women
- Finasteride, an oral prescription medication for men which blocks the formation of the active male hormone in the hair follicle
- Hair restoration surgery
Alopecia areata is an autoimmune condition in which the immune system, for unknown reasons, attacks the hair follicle and causes hair loss. The condition is common, nearly 2% of the US population (about 4 million people) will develop alopecia areata in their lifetime. This affects individuals of all ages, but is most common in children. Affected persons are usually otherwise healthy. This disease causes small, smooth, round patches of hair loss affecting the scalp and/or other body hair including eyebrows and eyelashes. Rarely it can result in complete loss of scalp and body hair. In most cases the hair regrows spontaneously, though sometimes it may last for many years. Several treatments are available to help stimulate hair growth and reduce inflammation. Treatments include:
- Corticosteroid injections in the scalp where the hair loss occurred
- Topical corticosteroids
- Topical sensitizing agents such as DPCP or squaric acid
Several months after a severe illness or major surgery, you may experience sudden loss of a large amount of hair. This is due to stress on the body which causes some of the hair to shift from the growth (anagen) phase to the resting (telogen) phase of the hair growth cycle. This causes a dramatic shedding of the hair. In most cases, this is temporary and resolves in a few months on its own. Some causes of of telogen effluvium include:
- High Fever, Severe Infection
- Major Surgery/Chronic Illness
- Medication – This type of hair loss improves when you stop taking the medicine. Medicines that can cause hair loss include: blood thinners, gout medication, chemotherapy drugs, excessive vitamin A supplements, birth control pills and antidepressants.
- Pregnancy – Many women notice hair loss about 3 months after they’ve had a baby. Hair loss after pregnancy can be caused by a number of factors and can be related to blood loss and hormonal and insulin imbalance after delivery. Generally, when the hormones return to pre-pregnancy levels, the normal cycle of growth and loss begins again.
- Discontinuation of birth control pills
Certain hairstyles and hair treatments can cause hair loss. Many men and women use chemical treatments on their hair, which can cause inflammation and scarring of the hair follicles. This include dyes, tints, bleaches, straighteners, and permanent chemicals. Excessive heat or hot oil treatments applied to the hair can also cause hair breakage. If hair becomes brittle from chemical treatments, it is best to discontinue use of these agents until the hair is allowed to grow out. Certain hair styles taht pulls the hair such as pigtails, cornrows, or tight hair rollers can also cause a certain type of hair loss called traction alopecia. If the pulling is stopped before scarring of the scalp develops, your hair will grow back normally. However, scarring can cause permanent hair loss.
Certain Fungal infections involving the scalp can cause hair loss. When treated with antifungal medicines, normal hair growth returns.
Trichotillomania (Hair Pulling)
Trichotillomania is most common in children, though it may occur in adulthood as well. Individuals may unconsciously pull on their hair, resulting in unusual patterns of hair loss on the scalp, eyebrows or eyelashes. This may simply represent a bad habit, but occasionally may be a sign of a more serious psychological problem.
Underlying Systemic Disease
Hair loss may actually be an early sign of a disease, so it’s important to seek the cause of sudden hair loss by seeing a dermatologist. This usually involves a complete physical exam and taking a thorough history. In some cases, blood tests or a biopsy (taking a small sample of cells to examine under a microscope) of your scalp may be needed.
Some causes include:
- Iron deficiency anemia
- Malnutrition (insufficient protein intake)
- Hormonal problems – An underactive or overactive thyroid gland may cause your hair to fall out. Treating thyroid disease should reverse this. An imbalance in male or female hormones can also cause hair loss. Correcting the imbalance may stop your hair loss.