The redness of half of the glans may be caused by glansitis, allergy, external forces, the patient should seek medical treatment in time to clarify the cause of the disease and then carry out appropriate treatment. 1. Glans inflammation: glans inflammation caused by infection, irritation, trauma, etc. will cause half of the glans to be red, and the patient will also have localized erosion, painful urination and itching. 2. Allergy: If the patient wore new underwear or used new condoms before the redness of the glans, it should be considered that it is caused by allergy. 3. External force: If you have rubbed or bumped your glans hard before the redness of half of the glans, you should consider that it is caused by trauma. All of the above medications should be used under a doctor’s supervision.