Aloe vera (AV) is suggested to be beneficial in treating irritable bowel syndrome (IBS) symptoms, but no scientific trials exist to confirm this. We aim to assess the efficacy of AV on IBS in refractory secondary care patients. Patients with IBS were randomised to receive AV or matching placebo for a month. Symptoms were assessed at baseline, 1 and 3 months. Fifty-eight patients randomised, 49 completed the protocol to 1 month and 41 to 3 months. Eleven of thirty-one (35%) AV patients, and 6 of 27 (22%) placebo patients responded at 1 month (p = 0.763). Diarrhoea predominant patients showed a trend towards a response to treatment at 1 month (10/23 V 2/14, p = 0.07). There was no evidence that AV benefits patients with IBS. However, we could not rule out the possibility that improvement occurred in patients with diarrhoea or alternating IBS whilst taking AV. Further investigations are warranted in patients with diarrhoea predominant IBS, in a less complex group of patients.