You should reconsult with your doctor to rule out the following possible causes -
'Perfumes, chemicals, or dye on toilet paper can cause an allergic reaction.
Moisture from sweat or diarrhea may cause itching. If the anal skin
stays wet, the skin
begins to break down.
Some foods irritate the anus when they are expelled during a bowel movement. The most common culprits are caffeine, chocolate, beer, nuts, dairy products, and spicy food.