Armpit odor may be caused by external factors, genetic factors, sweat gland secretion, mental nervous system factors. 1. External factors: summer weather is hot, indoor and outdoor temperatures are relatively high, which can easily lead to a lot of underarm sweating secretions, bacterial decomposition will produce ammonia, a pungent odor. Stress can also lead to a lot of sweating, local diphtheria-like bacillus decomposition of sweat, will produce a noticeable odor. 2. Genetic factors: armpit odor and heredity have a direct relationship, there is a family aggregation, such as parents who have armpit odor, due to genetic factors, their children may also have armpit odor. 3. Excessive secretion of sweat glands: there are sweat glands in the armpit area, after puberty, the hormone level changes in the body, the structure and number of sweat glands increase significantly, and sweat secretion is exuberant, which is easy to induce armpit odor. 4. Psycho-neurological factors: nervous system disorders lead to secretion system abnormalities, may also induce armpit odor. Certain metabolic diseases, such as phenylketonuria patients, sweat may have odor. It is recommended that patients pay attention to personal hygiene, light diet, reduce spicy stimulating food, avoid smoking and drinking. If necessary, go to the hospital dermatology department to understand the cause.