There are many reasons for the occurrence of hard lumps on the side of the anus: first, it may be a perianal abscess, due to diarrhea or prolonged squatting or sitting, and a diet of spicy and stimulating foods, which sometimes leads to an infection of the anal glands. The infection then spreads along the anal canal and rectum to the perianal area, resulting in a perianal mass that is visible and painful to touch. If an abscess is formed, there will be a local fluctuating sensation, and a perianal ultrasound can make a clear diagnosis. The second one is that the mixed hemorrhoids have been squatting and sitting for a long time, and after eating a lot of stimulating foods such as chili peppers and drinking alcohol, it will lead to the nucleus of the hemorrhoids to bruise and swell, and the hemorrhoid veins to stagnate, thus forming a thrombus. If there is a thrombosed hemorrhoid, it may appear as a hard lump on the side of the anus that is painful to touch and purple in color. The third, if there is anal canal cancer, anal canal malignant tumor will be manifested as a hard mass around the anus, sometimes the surface is cauliflower-shaped, pathological biopsy can be clearly diagnosed, so there are many causes of hard masses on the side of the anus, should be timely and symptomatic treatment.