Wearing underwear always feels painful down there, mainly considered to be related to factors such as over-tightening of underwear, allergy, reproductive system diseases and so on. 1. Too tight underwear: If the underwear is too tight, it will cause some pressure on the reproductive organs, leading to poor blood flow, which in turn will cause painful symptoms. 2. Allergy: the material of underwear is not comfortable, leading to allergy in the lower body, which can cause local pain, itching, rashes and other uncomfortable symptoms. 3. Reproductive system diseases: male epididymitis, orchitis and female vulvovaginitis and other diseases, after wearing underwear, can cause pressure on the affected area, exacerbating the condition, triggering pain and other symptoms in the lower body. Such symptoms may also be related to other causes, and it is recommended to consult a doctor as soon as possible to confirm the cause of the disease and carry out treatment under the guidance of the doctor.