Many small bumps in the coronal groove of the penis are associated with diseases such as penile pearly papules, bacterial infections, eczema, allergies, and sexually transmitted diseases. 1. Penile pearly papules: it is a benign tissue proliferative skin disease, the cause of which is not clear, and it can appear in the coronal groove as tightly arranged small bumps. 2. Bacterial infection: it can lead to localized dermatitis, which in turn can lead to pimples, itching and other symptoms. 3. Eczema: it can lead to the appearance of pimples of the size of a pinhead to a grain of rice in the affected area, accompanied by intense itching. 4. Allergy: If the material of underwear is not suitable, it can lead to local skin allergy, and pimples, itching and other symptoms. 5. Sexually transmitted diseases (STDs): such as second-stage syphilis, which can lead to syphilis rash in the genital organs and other areas. In addition, penile coronal candida-like papulosis can also cause this symptom, only by this symptom, can not accurately diagnose the condition, it is recommended that the patient timely medical examination, diagnosis of the cause of the disease. So that it can be timely targeted treatment.