Men with erythema on the head of the penis without abnormal sensation may be caused by glansitis, fixed drug rash, syphilis and other diseases. 1. glansitis: the cause is mainly related to factors such as long foreskin, candida infection, friction and so on. The patient’s glans will appear erythema, edema and other symptoms. 2. Fixed drug rash: often caused by oral sulfonamides or analgesics, etc.. It can occur on the head of the penis, local erythema, there may be erythema, blisters and other damage, often broken vesicles, the next time you take the drug can reappear, to carefully ask the medical history. 3. Syphilis: the cause of the disease is mainly caused with syphilis spirochete infection, promiscuity, unprotected sex and other factors can also induce the disease. Patients early penis, glans and other parts of the erythema will appear, usually no conscious symptoms. There are many reasons why men have erythema on the head of the penis without abnormal sensations, and it is recommended to go to a regular hospital to clarify the cause of the disease.