Sweating underarms with a sour odor may be physiological reasons, but also can be considered related to stinky sweating. 1. Physiological reasons: summer weather is hot, through sweating can regulate body temperature. If you don’t wash and change your clothes in time after sweating a lot in your armpits, ammonia can be produced after fermentation and decomposition, which can lead to a sour odor of sweat in the armpits, which is a normal situation. Through timely cleaning, keep the armpits dry, clean, change clothes in time, the odor can be eliminated. 2. Hyperhidrosis: If the sweat is relatively large, heavy odor, yellowish sweat color, but also to understand whether it is related to hyperhidrosis. Patients with hyperhidrosis, the sweat glands in the armpits sweat more, may produce obvious odor. It can be treated with topical antiperspirant, local injection of botulinum toxin, or minimally invasive surgery under the guidance of a doctor. Axillary sweating with obvious odor, it is recommended to pay attention to personal hygiene, if it is caused by pathological factors, it is recommended to go to the hospital dermatology department, under the guidance of the doctor.