Practice good personal hygiene, using a mild, non-colored, non-perfumed soap (just in case the soap is causing an allergy). Choose cotton underwear in preference to synthetic. Some embarrassing itching is caused by haemorrhoids (piles). A good drugstore will have creams and pessaries for this common condition.
If the itching is associated with any kind of discharge or a sore, you should tell a doctor. If not, then you could try changing your brand of toilet paper, preferably unscented. Is your underwear or outer clothing too tight? Have you recently changed detergents or bath soap?
You might try cortizone cream get the strongest they have over the counter, You also might want to have your doctor check you for pin worms or Hemmorodes I know the worms seem embaressing but believeme if you have children they are very common and easy to cure.
Treatment for rectal itching often includes use of an ointment or cream containing hydrocortisone or zinc oxide and an antihistamine to help relieve the itching until the topical medications have a chance to become effective. Seek medical care if itching persists more than 6 weeks.