The embryonated eggs of the porcine whipworm Trichuris suis ova (TSO) might have a role in the treatment of IBD. William Sandborn and colleagues investigated the safety and tolerability of a single dose of TSO in patients with Crohn's disease. The researchers conducted a randomized, double-blind, placebo-controlled, dose-escalation study in 36 patients. The patients received either 500, 2,500 or 7,500 viable embryonated TSO and were assessed 1, 3, 5, 7, 9, 11 and 14 days after dosing. Patients were assessed again at 1, 2 and 6 months. The main findings from the study are that a single dose of TSO including up to 7,500 ova was well tolerated and that no short-term or long-term treatment-related adverse effects were noted.