It would seem to me that you have a condition that is known as pruritus ani basically translates to itchy anus.
Pruritus ani means a chronic (persistent) itchy feeling around the anus. The main symptom is an urge to scratch your anus which is difficult to resist. The urge to scratch may occur at any time. However, it tends to be more common after you have been to the toilet to pass faeces, and at night (particularly just before falling asleep). The itch may be made worse by heat, wool, moisture, leaking, soiling, stress, and anxiety.
About 1 in 20 people develop pruritus ani at some stage. It is common in both adults and children.
This is a common situation. The following tips often help to stop the itch.
Avoid any potential irritants
Stop using scented soaps, bubble bath, perfume, etc, near the anus.
Use plain, non-coloured toilet tissue. Wipe your anus gently after passing faeces.
Could any foods or medicines be causing the itch? Try avoiding for a while the foods and drinks listed above (such as fruits and tomatoes). Do you take laxatives regularly? Some may be leaking onto the anal skin.
Pay special attention to hygiene around the anus
Wash the anus after going to the toilet to pass faeces. The aim is to clear any remnant of faeces which may irritate the skin.
When washing around the anus it is best to use water only. If you use soap, use bland non-scented soap.
When you are not at home, use a moistened cloth or a special moistened tissue to clean the anus. You can buy moistened tissues from pharmacies.
Bath or shower daily. If possible, wash the anus with water only. If you use soap around the anus, rinse well.
Change your underwear daily.
Avoid excessive moisture around the anus
After washing, dry around the anus properly by patting gently (rather than rubbing) with a soft towel. Even better, use a hair dryer, especially if your anal skin is hairy.
Do not put on underwear until the anus is fully dry.
Wear loose cotton underwear (not nylon). Avoid wearing tight fitting trousers. If possible, do not sit for long periods, and try not to get too hot. The aim is to allow air to get to the anus as much as possible, and for it not to get too sweaty.
If you sweat and moisture gathers around your anus, put a tissue in your underwear to absorb the moisture.
Consider the 'itch-scratch cycle'
Scratching can make the itch worse - which makes you want to scratch more, etc.
As much as possible, try not to scratch. This is especially difficult at night when the itch tends to be worse when you are trying to get to sleep.
You may also scratch in your sleep without realising. To help this:
Keep your fingernails short to limit any damage done to the skin by scratching.
Consider wearing cotton gloves at night to prevent sharp scratching with fingernails.
An antihistamine medicine that makes you drowsy may be worth a try at bedtime. Your doctor will advise.