The red rash on the glans is considered to be caused by glansitis, condyloma acuminatum, penile cancer, drug dermatitis and other diseases. 1. glans: mostly due to pathogen infection, in addition, external adverse stimuli, autoimmune skin disease can also be triggered by glans, after the disease, the patient’s foreskin, glans will appear red, swollen, pain, and visible glans skin mucosa with red rash, ulcers, serious condition, but also cause fever, inguinal lymph nodes swelling and other systemic discomforts. 2. Condyloma acuminatum: also known as genital warts, occurring in sexually active young and middle-aged, male patients can be due to HPV virus infection leading to the glans, penis, perineum, anus and other parts of the reddish pimples, with the pimples gradually grow, can form a crown, cauliflower-shaped warts. 3. Penile cancer: If there is malignant tumor in male penis, if the foreskin can be turned up, the glans can be seen red patches and papules, in addition, there will be foul smell under the foreskin, which can be accompanied by bleeding or pus. 4. Drug dermatitis: also known as drug rash, refers to the adverse skin and mucosal reactions caused by drugs (such as oral, injection, inhalation, etc.), different drugs can cause different types of drug rash, such as sulfonamides, barbiturates and other drugs, can cause the oral cavity, genital skin and mucous membrane (such as the glans, etc.) and other parts of the skin, the appearance of red patches, and there can be a mild itching, stop the drug, the symptoms can be relieved. In addition, there are many other reasons that can cause red rash on the glans, it is recommended that patients go to the hospital in time, after clarifying the cause of the disease, receive treatment as soon as possible.