Swelling and pain in the lower body usually refers to the swelling and pain in the lower abdomen and perineum, and the common causes are as follows: 1. Women: such as vaginitis, vulvovaginitis, or even skin diseases in the pubic area, sexually transmitted diseases, etc., which may cause swelling and pain in the vulva, i.e., the lower body, in women; 2. Men: it may be inflammation of the vulva, such as priapism, penile circumcision, and glans, which may also cause swelling and pain in the lower body.