AbstractOBJECTIVES: Patients with chronic constipation due to food hypersensitivity (FH) had an elevated anal sphincter resting pressure. No studies have investigated a possible role of FH in anal fissures (AFs). We aimed to evaluate (1) the effectiveness of diet in curing AFs and to evaluate (2) the clinical effects of a double-blind placebo-controlled (DBPC) challenge, using cow's milk protein or wheat.METHODS: One hundred and sixty-one patients with AFs were randomized to receive a "true-elimination diet" or a "sham-elimination diet" for 8 weeks; both groups also received topical nifedipine and lidocaine. Sixty patients who were cured with the "true-elimination diet" underwent DBPC challenge in which cow's milk and wheat were used.RESULTS: At the end of the study, 69% of the "true-diet group" and 45% of the "sham-diet group" showed complete healing of AFs (P<0.0002). Thirteen of the 60 patients had AF recurrence during the 2-week cow's milk DBPC challenge and 7 patients had AF recurrence on wheat challenge. At the end of the challenge, anal sphincter resting pressure significantly increased in the patients who showed AF reappearance (P<0.0001), compared with the baseline values. The patients who reacted to the challenges had a significantly higher number of eosinophils in the lamina propria and intraepithelial lymphocytes than those who did not react to the challenges.CONCLUSIONS: An oligo-antigenic diet combined with medical treatment improved the rate of chronic AF healing. In more than 20% of the patients receiving medical and dietary treatment, AFs recurred on DBPC food challenge.