Is it itching on the inside, outside or both?
If parasites are causing the itching, stick a clove of garlic in your butt. Works even better if you scrape/scratch it with a knife so the juices can flow. Or put some green Black-Walnut hull, Wormwood and cloves in an empty gel cap and insert this in your anal sphincter. It will be hard to hold at first. If it makes you poop, put in some more after you go to the bathroom. If it makes you poop again, put in some more. Keep doing that until you can hold it.