The redness of the foreskin may be a physiological phenomenon, or it may be caused by infectious factors, allergic factors and other reasons. 1. Physiological phenomenon: penis in the state of erection, masturbation, sexual life and other reasons, will cause the penis, foreskin glans congestion, may cause the phenomenon of red foreskin. 2. Infectious factors: bacterial, trichomonas, fungal infections caused by phimosis, can also cause redness of the foreskin, and in some cases there will be a rash, itching and other symptoms. 3. Allergy: contact dermatitis, drug rash and other allergic causes, can also cause redness at the foreskin, and some will also cause prominent skin rash, itching and other manifestations. To summarize, the redness of the foreskin, there may be other reasons, it is recommended to go to the hospital for examination, to clarify the cause of the disease, and follow the doctor’s instructions for treatment.