Swelling and pain in the lower part of the man after intercourse may be caused by acute injury, circumcision and allergic factors. 1. Acute injury: during intercourse, men use too much force, resulting in localized damage to the penis, there will be pain and swelling after intercourse, may also be accompanied by redness and subcutaneous bruising. 2. Gluteitis: men themselves have gluteitis, after sex, due to frequent stimulation, may lead to gluteitis aggravation, will make the local pain and swelling symptoms, accompanied by itching. 3. Allergic factors: during sex, men use poor quality condoms, resulting in an allergic reaction in the penile area, which can lead to localized redness, swelling and pain, accompanied by intense itching. After coitus, the man’s bottom is swollen and painful, it is recommended to consult a doctor for examination, to clarify the specific causes of the disease, and timely treatment.