A pimple on the penis may be caused by diseases such as folliculitis, sebaceous cysts, condyloma acuminatum, penile cancer, etc., but the specific situation needs to be judged under the guidance of a doctor. 1. Folliculitis: it is usually an inflammatory lesion caused by bacterial infection and other factors, due to the stimulation of inflammation, it may lead to the phenomenon of a pimple on the penis. 2. Sebaceous cysts: usually due to the sebaceous gland duct obstruction after the accumulation of glandular contents, resulting in the phenomenon of a pimple on the penis. 3. Condyloma acuminatum: it is usually an infectious disease caused by human papilloma virus infection, and the penis may develop a pimple under the stimulation of viral infection. 4. Penile cancer: If the patient suffers from penile cancer, the symptom of a pimple growing on the penis may also appear. When men have a pimple on penis, it may also be related to other factors, so it is recommended to go to hospital in time for clear diagnosis and standardized treatment.