Telogen effluvium is a common nonscarring alopecia characterized by excessive hair shedding over the entire scalp. At any given time, approximately 90% of normal scalp hair is in the anagen (growth) phase, and 10% is in the telogen (shedding) phase. In telogen effluvium, there is an increase in the percentage of follicles in the telogen phase of the hair growth cycle to greater than 20%. This premature transition of hair follicles to the telogen phase may occur in response to acute physical, physiological, or psychological stress, systemic illness, or hormonal changes (including pregnancy). Causes include major surgery, high fevers, drugs, anorexia and bulimia nervosa, fad diets (especially low-protein diets), childbirth, heavy blood loss, nutritional deficiency (especially protein, iron, and zinc), and serious illness (thyroid disease, renal disease, liver disease, inflammatory bowel disease, systemic lupus erythematosus, lymphoproliferative disorders). Telogen effluvium is the most common alopecia associated with systemic illness.

Drugs implicated include acitretin, isotretinoin, high-dose vitamin A, beta blockers (metoprolol, nadolol, propranolol, and topical timolol), bromocriptine, captopril, cimetidine, antidepressants (fluoxetine), sulfasalazine, anticonvulsants (eg, valproic acid and lamotrigine), interferons, antihyperlipidemic drugs, diabetic drugs, androgens, oral contraceptives, anticoagulants (warfarin, heparin), albendazole, and chemotherapeutic agents. Drug-induced hair loss is usually reversible after cessation of medication use. Cases have been identified after viral infections, such as human papillomavirus (HPV) vaccination in children, human immunodeficiency virus infection, and dengue fever in adults.

The interval between the inciting event or exposure and the shedding is generally weeks to a few months. In adults, the cause is often never identified. In children, etiology may be easier to discern. Telogen effluvium may occur as a normal physiological phenomenon in this age group.

Telogen effluvium primarily affects women in the fourth to seventh decade of life. Patients present complaining of a sudden increase in hair shedding from the root with a small white hair bulb, often after showering or during combing. The hair loss occurs uniformly over the entire scalp and is usually asymptomatic, without stinging or pruritus. Hair loss usually exceeds 150 hairs daily and may continue for 6-12 months. Less commonly, a chronic form of telogen effluvium can last several years. While it may occur after common triggers of telogen effluvium, it may begin without a clear etiology.

Telogen effluvium itself is a benign and self-limited condition, although its presence may provide a clue to an underlying disease.

Related topics: Drug-induced alopecia, Anagen effluvium