A clear blister on the male glans in the coronal groove can be considered to be a disease such as genital herpes, eczema or glans phimosis. 1. Genital herpes: when the herpes simplex virus infects the genitals and perianal skin, it can cause scattered or clustered small blisters on the male glans, coronal groove, etc., and vesicles or ulcers can be formed after 2 to 4 days, which can be scabbed over and healed. 2. Eczema: when eczema forms on the vulva, scrotum and other places due to a variety of factors, pimples, papules or blisters may appear, due to localized intense itching, blisters rupture, leaving oozing and vesicles. 3. Circumcision: In the penis glans and foreskin due to poor local cleaning or circumcision and other factors, can be formed in the local foreskin scale, which can trigger inflammation of the glans and foreskin, so that the glans appears itching, redness, swelling, congestion, but also the formation of rashes. When the male genital area of the rash, it is recommended to go to a regular hospital specialist to remove the cause of the disease in a timely manner, and to prevent the emergence of complications.