Hair is formed from hard keratin by the matrix cells of the hair follicles which are invaginations of the epidermis. The extra-follicular hair is a dead structure and no procedures applied to it will have any stimulating effect on its growth. There are two types of hair, the fine, downy, vellus hair which is present over the whole body except the palms and soles, and terminal hairs, the thick, pigmented hairs which are present on the scalp, beard, eyebrows, eyelashes, axillary, pubic and body regions.
Hair growth occurs in cycles and hair in different regions has a different growth cycle. A long growing phase (anagen) is followed by involution of the follicles and a short resting phase (telogen). Resting hairs make up 5—15 per cent of the total of 100,000 hairs on the human scalp and the daily loss of scalp hair is 20-100. Scalp hair grows about 2 mm weekly and the growing phase of any one hair is 2 to 3 years, though exceptionally it may be very much longer. Terminal hairs elsewhere on the body have a shorter growing phase than those on the scalp. The high speed of growth of the scalp hair makes it more susceptible to damage from systemic disease, toxic drugs and radiation.
Hair growth is dependent on hormone influences and hair in different regions is dependent on different hormone stimulants. Oestrogens are a stimulant to scalp hair growth in women and androgens have the reverse effect. During pregnancy there is a delay in telogen hair fall so that scalp hair becomes thicker than normal. A sudden hair fall occurs in the puerperium and this is most marked in the frontal areas. Hair is also lost after the menopause and there may be at the same time an increase in facial hair growth. Axillary and pubic hair is dependent in women on adrenal androgens and the hair is lost in Addison’s disease, whilst in men the hair is not lost as testosterone alone can maintain it. In contrast, testosterone has a deleterious effect on male scalp hair and eunuchs do not develop male pattern bladness. In hypothroidism and in hypoparathyroidism, the hair on the scalp and the whole body becomes dry and sparse. Therapeutic cortiscosteroids behave like androgens and overgrowth of vellus hair is an undesirable side effect.
Alopecia, or hair loss, can occur as a result of changes in the hair follicles which are invisible or from manifest disease of the scalp which detroys the hair matrices. So much psychological significance is attached to the possession of luxuriant scalp hair that a complaint of thinning hair is a frequent one. It is important to assess that the symptoms are real since many women do not appreciate that the loss of 100 hairs a day is normal and as part of anxiety state believe that they are going bald.
To determine whether the complaint of hair loss is genuine patients should be asked to collect and count hairs lost on the comb the day before washing the head, after washing and on two succeeding days, 4 days in all. An average daily loss of over 100 is abnormally high.
Hair loss can be divided into acute hair fall and a gradual loss which leads to a pattern of baldness.
Acute hair loss. (Alopecia areata.) This is the most common cause of acute hair fall. It frequently starts in childhood and there may be a family history. Hair is lost over clearcut round areas of the scalp or beard.
The bald patches may be faintly pink, but otherwise the scalp appears normal and does not scale. In the stage of active hair fall, broken stumps called exclamation mark hairs are present at the spreading edge of the bald patch but they are absent if the lesion is not extending. Spontaneous recovery takes place in over 60 per cent of first attacks but the prognosis worsens with second and third attacks. Rarely, alopecia areata extends to the whole scalp and even all the hair on the body, and in this instance recovery is unlikely. A bad prognostic sign is superficial pitting and ridging of the finger nails. The cause of alopecia areata is unknown but it is probably an autoimmune process as it is associated with vitiligo, thyroid and endocrine deficiency disorders. It is also seen more frequently in Down’s syndrome. There is some association with emotional stress but this is by no means conclusive. Since the majority of patients with alopecia areata recover spontaneously in 3—6 months, firm reassurance with, if considered desirable, a harmless local placebo is all that is required. Injection of corticosteroids either with a hypodermic needle or multiple needleless injector into a patch of alopecia areata is usally followed by regrowth of hair and this may be used to encourage both the hair and the patient if recovery is delayed.
The application of betamethasone (Betnovate) scalp application or fluocinolone acetonide, (Synaiar Gel) are more acceptable to the patient though less effective than injections. In our opinion, systemic steroids, though immediately effective in alopecia totalis, are not justified and a wig is to be preferred.
Hair loss from systemic disease
Diffuse hair fall some three months after a severe febrile illness is common and it may also occur after extensive surgical procedures. Regrowth of hair is invariable in three to four months. Less commonly, hair fall may occur with severe emotional stress. Hair loss in a patient with rheumatoid arthritis may indicate the onset of disseminated lupus erythematosus and though now rare, syphilis should be excluded in the diagnosis of patchy alopecia. The antimitotic drugs, and heparin and dextran all cause profuse alopecia. A lowered serum iron either due to frequent blood loss from disease or from repeated donation of blood transfusions may cause diffuse hair loss.
Overprocessing hair loss
The keratin of the hair shafts may be damaged by waving solutions, bleaches or heat of the hair dryer. Such overprocessing causes a sudden hair loss from fracture of many of the hairs and the diagnosis can be made easily by the examination of the end of the stumps which will show ragged fractures. The condition recovers spontaneously.
As has already been mentioned, a male pattern of baldness and frontal recession may appear in women about three months after childbirth and this can return more severely in successive pregnancies. Regrowth is already taking place when hair loss is noticed and no treatment other than reassurance is necessary.
Postinflammatory hair loss
Temporary hair loss occurs after the scalp has been affected by sepsis. A disc devoid of hair may form around a recent boil. Considerable hair loss may follow if the scalp is severely affected by psoriasis. When the scaly patch of psoriasis has been cleared by treatment hair recovery then takes place.
Male pattern baldness (Chronic hair loss)
Loss of hair on the frontal region and over the vertex may begin soon after puberty in males. Once begun, baldness progresses with phases of active hair loss followed by static periods. Increased dandruff, erythema and irritation occur coincident with the hair fall. This appears to be an associated androgen effect and not the cause of the hair loss. Hair follicles can be transferred by grafting from the occipital to the frontal region and the resultant hairs will continue to grow. This suggests that the growth factor for occipital hair and frontal hairs is different. It is not a practicable treatment for male baldness and prognosis for hair recovery is hopeless. There is, of course, a strong genetic factor in male baldness and patients should be discouraged from seeking a medical cure and advised to accept their fate philosophically.
Hair loss in women
Thinning of the scalp hair over the vertex and top of the head is common in menopausal women and marked baldness may occur in extreme old age. In recent years, more young women have complained of early baldness, which may reflect the general increased interest in hair styling rather than an absolute increase in the condition. Investigation rarely reveals any endocrine disorder although hypothyroidism is responsible for a small number. Excess of virilising hormones is extremely rare but must be excluded. The hair loss is similar to male baldness and like it, has a strong genetic factor. Fortunately, the baldness is only partial and rarely noticeable to others than the patient. This is however little comfort to the patient who is frequently very distressed. Advice to avoid nylon hair brushes, massage and hair styles, which place a physical strain on the hair is all that can be offered. Applications to the scalp of creams containing ovarian hormones (theoretically sound treatment) are valueless.
Destruction of hair follicles occurs with any damage to the full thickness of the scalp. Scars from burns, mechanical injury, deep pyogenic infection and radiation can be diagnosed from the history.
A number of rare skin diseases, scleroderma, lichen planus, lupus erythematosis, lupus vulgaris, produce permanent scarred alopecia but they are an insignificant group and need not concern us further.
Localised overgrowth of hair may occur in or over intradermal naevi and over the spine where it can indicate developmental defects. Excessive hair growth of the face, body and limbs of women is a common and distressing complaint. Some increase of facial hair growth in menopausal women has already been mentioned and hirsuties can occur in metabolic disorders such as porphyria. However, the great majority of women who suffer from overgrowth of facial hair do not suffer from any demonstrable endocrine or other disorder and the trait is often familial and racial. A probable explanation is an inherited metabolic abnormality of vellus hair follicles which give rise to terminal hairs as a response to normal hormone levels. It is important not to miss some source of virilising hormones but if the menstrual history is normal, a hormonal disorder is unlikely. No hormonal treatment can control essential hirsuties and medical treatment is primitive and unsatisfactory. Destruction of hair follicles by electrolysis is effective for small groups of hairs but is impracticable for a well developed beard. Chemical depilatories give a good cosmetic result but often produce skin irritation. Frequent rubbing down of the hairs with fine abrasive paper is acceptable to many women who do not wish to shave. The technique has to be learnt and the patient encouraged in the early stages.