Armpit is a common name, clinically known as the armpit, summer armpit redness, swelling and pain is usually due to rubella, cornu rashes, axillary lymphadenitis and other diseases. 1. Eraser rash: axillary skin folds more, coupled with higher temperatures in the summer, armpit sweating increased, which is easy to trigger between the eruption, resulting in localized axillary skin erythema, swelling, and will be accompanied by itching, pain and other discomforts. 2. Corns: The human body produces a lot of sweat in summer, if the sweat is not timely, can be impregnated with local skin or local skin sweat duct obstruction, triggered by corn rash, this disease occurs in the armpit, neck, elbow and other parts of the skin lesions are elevated blisters or pimples, and there is a red halo around the area, accompanied by burning pain, itching. 3. Axillary lymphadenitis: It is caused by the invasion of the axillary lymph nodes by pathogenic bacteria from the skin, mucous membranes or nearby infectious foci, resulting in the patient’s armpits appearing enlarged, pressure and pain, and can be seen in the local skin redness and fever. In addition, there are many other causes can cause redness, swelling and pain in the armpit in summer, it is recommended that patients go to the hospital in time to find out the cause of the disease, and then receive treatment as soon as possible.