A lot of red blood on the glans during erection may be caused by glansitis, glans eczema, external stimulation and other reasons. 1. glansitis: external bacteria, viruses, mycoplasma, trichomonas and other pathogenic bacteria infection, resulting in inflammatory reaction of the glans, may cause a lot of red blood on the glans during erection. 2. glans eczema: infectious factors, allergic factors, physical factors and other causes of glans eczema, may also cause a lot of red blood on the glans during erection, may also cause glans mucosa oozing, redness, swelling, erosion, pain, itching and other symptoms. 3. external stimulation: for example, the glans is subjected to trauma and other stimuli, or excessive masturbation, frequent sex and other reasons caused by the expansion of capillaries, can also cause the glans a lot of red blood on the erection. There may be other reasons for the red blood on the glans during erection, it is recommended to go to the hospital in time for examination, to clarify the cause of the disease and follow the doctor’s instructions for treatment.