Anal sinusitis sit down pain is mainly due to anal sinusitis itself, may also be due to anal sinusitis secondary infection caused by perianal eczema, perianal abscess. 1. Anal sinusitis: refers to the acute or chronic inflammation of the anal sinus and anal valve caused by bacterial infection. It is mostly characterized by incomplete defecation, crushing and painful sensation. The initial stage of sinusitis will not show obvious pain, but when you sit down, it will compress the inflamed sinus, causing localized swelling, and with the contracture of the anal sphincter, it will make the pain worse. 2. Perianal eczema: sinusitis often causes localized anal swelling, accompanied by purulent or mucous secretion overflow, long-term anal moisture, itching, will be secondary to perianal eczema, resulting in perianal erythema, papules, blisters, etc., sit down when the papules, blisters, etc., compression of the perianal area will lead to pain. 3. Perianal abscess: When inflammation and edema occur in the sinuses, the normal secretion of the anal glands will be blocked, leading to perianal infection and causing perianal abscess. When you sit down suddenly, the mass presses and stimulates the perianal nerve causing pain. If you are suffering from sinusitis and have pain when sitting down, it is recommended to go to the hospital, do not self-medication, delay the condition, under the guidance of the doctor active diagnosis and treatment.