The partial or complete whitening of hair is called canities.

bubble_chart Etiology

White hair is caused by a decrease in melanin production due to fewer melanocytes and melanosomes or reduced tyrosinase activity.

Gray or white hair in the elderly is a physiological phenomenon resulting from the progressive loss of tyrosinase activity in melanocytes, leading to the disappearance of pigment in the hair shaft. Gray hair has a normal number of melanocytes but reduced melanin, while white hair also has fewer melanocytes.

Premature graying or whitening of hair before old age often has a family history and manifests as an autosomal dominant inheritance. It can also be seen in certain syndromes, such as progeria, Rothmund syndrome, Werner syndrome, Waardenburg syndrome, dystrophia myotonia, and Böök syndrome.

Generally, severe diseases such as pernicious anemia, hyperthyroidism, cardiovascular diseases (e.g., coronary heart disease, myocardial infarction), peripheral arterial diseases, hypertension, subcutaneous nodules, cold-damage disease, and syphilis can lead to white hair.

bubble_chart Clinical Manifestations

Hereditary white hair is usually present at birth or appears rapidly during childhood. It includes conditions such as albinism, which involves generalized whitening of hair, and piebaldism, which involves localized whitening of hair.

Senile white hair (Canities Senilis) often begins at the temples and gradually spreads to the crown of the head. Over the years, beard, nasal hair, etc., also turn gray, but chest hair, pubic hair, and armpit hair remain unchanged even in old age.

Premature white hair in young or middle-aged individuals (Canities prematura) starts with only a few white hairs, which gradually increase over time.

bubble_chart Treatment Measures

Currently, there is no specific and effective treatment, with hair dyeing being the primary method.