Swelling and pain in the lower body usually means swelling and pain in the genital area, which may be caused by the following reasons: First, if there is swelling and pain in the cystic penis, it may be caused by inflammation of the foreskin or glans, or swelling and pain caused by infection of the urinary system or urethra. Secondly, if the testicles of men are swollen and painful, it is usually due to epididymitis which causes local redness, swelling, heat and pain, and it is due to upper respiratory tract infection, such as viral infection or bacterial infection, or it may be that the virus of mumps has invaded the whole body and reached the location of epididymis through blood circulation and the appearance of epididymal inflammation. Thirdly, if a woman has vaginitis, the most common vaginitis is trichomonas vaginalis. In addition, if there is a painful protruding swelling in the perineum of the lower body, we must also exclude the possibility of hernia.