Half a peanut-sized lump under the scrotum without pain or itching may be caused by epididymitis, sebaceous cysts, etc., patients should seek medical attention in a timely manner to clarify the cause of the disease after treatment. 1. Epididymitis: most common in sexually active young men, mostly caused by bacterial infections, recurrent episodes will have half a peanut-sized lump under the scrotum painless, such people in the acute attack should be braked and bed rest, can be localized ice packs, and if necessary, the use of levofloxacin and other drugs for treatment. 2. Sebaceous cysts: half a peanut-sized painless hard lump under the scrotum may also be sebaceous cysts, generally no conscious symptoms, but secondary infection will have local redness and swelling and fluctuating sensation, can be surgically removed. There are other reasons that may cause the symptoms, patients who find hard lumps in the scrotum, it is recommended to consult a doctor in a timely manner, after clarifying the cause of the disease, under the guidance of the doctor for treatment.