International Academy of Cosmetic Dermatology
Hair loss may be called baldness, thinning hair, or the preferred Alopecia, from the Greek.
Contrary to popular belief, washing the hair daily, wearing a hat, and standing under the shower nozzle do not cause hair loss. Hair is dead tissue, and no amount of “hair food” will change the growth cycle.
Hair remains on the scalp for five to seven years. The hair then falls out, and the hair follicle replaces it. Hair grows approximately 0.1 mm per day, although there may be seasonal variations. The hair cycle is divided into growing (anagen – 85%), intermediary (catagen – 3-5%), and resting (telogen – 10-12%)
TYPES OF ALOPECIA
This is a condition of unknown cause where the hair follicle stops making hair. The hair bulb resembles an exclamation point. Alopecia areata usually lasts for six to twelve months. When the absence of hair is elsewhere in addition to the scalp, it is called alopecia totalis. When the entire body is involved, it is called alopecia universalis.
Treatment may be soothing; i.e. the use of topical steroids and/or intralesional steroids or irritating: i.e. short contact anthralin therapy or contact sensitization.
Male pattern baldness and female pattern baldness occur in over 50% of the population. Men begin to lose hair in their twenties, while the condition appears in women during or after the menopausal years. Although genetics may play a role, there is good evidence that dihydrotestosterone (DHT) is involved, the pathway being the conversion of testosterone to DHT by the enzyme 5-alpha-reductase (type I and II), due to alterations in androgen metabolism.
Available therapy includes topical minoxidil with the 5% solution being the most efficacious. Oral finasteride is useful in men, while aldosterone may be helpful in women. These drugs usually offer only 10% regrowth and probably work by preventing future hair loss.
Scarring alopecia may be due to a variety of diseases ranging from an infiltrative process (i.e. metastatic cancer, sarcoidosis) to trauma (i.e. burns and radiation) and infections.
Dissecting Cellulitis of the Scalp
Also called perifolliculitis capitis abscedens et suffodiens, this inflammatory cicatricial alopecia represents a bacterial infection that smolders in the skin of the scalp, resulting in scarring and pain.
Pseudopelade of Brocq
This noninflammatory alopecia presents with a moth-eaten pattern of hair loss, giving the appearance of footprints in the snow. There may have been an underlying infection that smolders and then dies out.
When there is a condition causing an increased metabolic rate, this condition can occur, usually three to four months after the event. Common reasons for shedding hair include pregnancy and the post-partum period. High fevers and sudden trauma can also lead to a loss of telogen hairs. The condition resolves itself in six to twelve months.
Traction and Chemical Alopecia
Vigorous brushing or tight weaving can lead to hair loss. It is the constant brushing that can be a problem. A similar scarring alopecia results from using hot combs where the oil drops onto the scalp.
Samantha Neves, MD
San Paulo, Brazil