Chronic constipation that is unresponsive to laxative treatment is a severe illness, but children unresponsive to laxatives have been successfully treated with an elimination diet. We report the first cases of refractory chronic constipation caused by food hypersensitivity in adults. Four patients with refractory constipation who were unresponsive to high doses of laxatives were put on an oligo-antigenic diet and underwent successive double-blind, placebo-controlled, food challenges (DBPFC). Routine laboratory tests, immunological assays, colonoscopy, esophago-gastroduodenoscopy and rectal and duodenal histology were performed. While on an elimination diet, bowel habits normalized in all patients and a DBPFC challenge triggered the reappearance of constipation. In comparison with another 13 patients with refractory constipation unresponsive to the elimination diet, observed over the same period, the patients with food-hypersensitivity-related constipation had the following characteristics: longer duration of illness (p < 0.03), lower body mass index (p < 0.03), higher frequency of self-reported food intolerance (p < 0.01), higher frequency of nocturnal abdominal pain and anal itching (p < 0.01). In patients with food hypersensitivity, hemoglobin concentrations and peripheral leukocytes were lower than those in controls (p < 0.03). The duodenal and rectal mucosa histology showed lymphocyte and eosinophil infiltration, and the duodenal villi were flattened in two cases. In adult patients, refractory chronic constipation may be caused by food hypersensitivity and an elimination diet is effective in these subjects.