The sudden itching of the anus is considered to be caused by the following conditions: 1. Consider anal eczema, which is a relatively difficult to cure skin disease and belongs to the skin metaplasia. It is easy to have recurrent episodes of this disease, and the itching is unbearable during the episodes. It is not allowed to scratch, you can use dermaplanin to apply to the affected area or inject dexamethasone. 2, consider pinworms, especially at night pinworms crawl out of the anus and lay eggs on the perianal skin, the itching sensation is more obvious. 3, consider the anal fissure caused, also accompanied by a stinging sensation and bleeding. 4, there may be anal sinusitis, hemorrhoids, anal fistula and other diseases caused, it is best to go to the anorectal department for anal finger examination The best thing to do is to go to the anorectal department for an anal finger test or anoscopy to determine the cause before dealing with it.