Pimples on penis may be caused by allergy, condyloma acuminatum, folliculitis, genital herpes and so on. 1. Allergy: If the patient has an allergic reaction, it can lead to pimples on the penis, for example, allergy to the material of the underwear, there will be an allergic reaction in the local area, which will lead to pimples on the penis and obvious itching sensation. 2. Condyloma acuminatum: pimples on the penis may be caused by condyloma acuminatum, condyloma acuminatum is a sexually transmitted disease caused by human papillomavirus infection, manifested as pimples, cauliflower-like or corns-like fleshy redundancies on the genitals or perianal and other moist parts of the body, with a rough and keratinized surface. 3. Folliculitis: pimples on the penis may be caused by folliculitis, when the penis hair follicles are infected by bacteria, there will be inflammatory papules, pus plugs can be seen in the center, accompanied by redness and swelling, and there will be obvious pain when touching. 4. Genital herpes: pimples on the penis may be caused by genital herpes, genital herpes is a sexually transmitted disease caused by the herpes simplex virus, manifested as blisters on the pubic area or perianal area, pain, fever, headache, fatigue and other symptoms. It is recommended that patients with symptoms of pimples on the penis, go to the hospital in a timely manner, to clarify the cause of the disease under the guidance of the doctor reasonable treatment.