Red and itchy testicular skin and penis may be related to eczema, atopic dermatitis, ringworm and other causes. 1. Eczema: the cause of eczema is complex, often as a result of the interaction between internal and external causes. If the testicular skin and penis can also have eczema, it can lead to redness, swelling, itching and other symptoms. 2. Allergic dermatitis: If the testicular skin and penis are exposed to allergenic substances, such as underwear containing chemical fibers, it will cause the body to undergo an abnormal immune response, resulting in redness and itching. 3. Ringworm: If the fungus infects the testicular skin and penile skin, it can lead to the appearance of ringworm on the skin, which can be manifested as redness and itching. There are many reasons for red and itchy testicular skin and penis, it is recommended that people with red and itchy testicular skin and penis go to the hospital in a timely manner, to clarify the cause of the disease, and standardized treatment under the guidance of the doctor.