The first of these is anal eczema, a condition in which there are bunches of small blisters at the anal opening, with a flushed base and itchy and painful sensation, which can cause the local skin to break down, bleed, ooze and become inflamed once scratched. It needs to be treated by applying glycopyrrolate and taking oral cephalosporin. Secondly, it may be a perianal abscess, which may be hard to the touch by pressure. And this blister inside the purulent discharge, can be pushed and also accompanied by pain and fever, serious cases can reach about 40 ℃, need to love for incision and drainage. Normally, it can also be a blister caused by inflammatory external hemorrhoids, and in severe cases, there may be enlargement, pain, and congestion of the hemorrhoid nucleus. Finally, it is not excluded that it is caused by conditions such as anal fistula, and it is best to go to the hospital for examination and treatment.