Derivatives of 5-aminosalicylic acid (5-ASA) used for the treatment of inflammatory bowel disease may induce acute pancreatitis of immunoallergic origin. 4-aminosalicylic acid (4-ASA) differs from its 5-ASA counterpart by the position of the NH2 group and has shown efficacy in ulcerative colitis. The risk of cross intolerance reaction between 5-ASA and 4-ASA has currently never been evaluated. We report three cases of 5-ASA-induced pancreatitis, with no recurrence of pancreatitis during subsequent treatment with 4-ASA enemas. We conclude that 4-ASA enemas are a safe and well-tolerated therapeutic alternative whenever 5-ASA-induced pancreatitis occurs.