Peppermint oil for irritable bowel syndrome: how it works and who should avoid it

Peppermint oil contains menthol, which relaxes smooth muscle. Cramping in irritable bowel syndrome involves the bowel wall contracting painfully, so a muscle relaxant that reaches the intestine makes biological sense. That is why enteric-coated capsules, which are designed to pass through the stomach and release the oil lower down, are the form studied for IBS.

Peppermint tea is not the same thing. It is much weaker and releases its oil in the stomach, so it should not be expected to behave like a capsule.

A 2022 review found that peppermint oil in enteric-coated capsules was better than placebo at improving overall IBS symptoms and reducing abdominal pain. The American College of Gastroenterology recommends it for symptom relief. In the UK, the NHS page on IBS treatment names peppermint oil alongside Buscopan for cramps and bloating, and loperamide for diarrhoea.

Benefits are for symptoms, not for curing the condition. Peppermint oil does not address the diet, stress and gut-brain factors that drive IBS, and it does not suit every person.

The NHS stresses there is no single diet or medicine that works for everyone with IBS. Practical steps include keeping a food and symptom diary, eating regular meals, limiting high-fat and spicy foods, using oats and soluble fibre sensibly and managing stress. Peppermint oil is something to try as part of that plan, ideally with advice from a pharmacist.

• Persisting symptoms despite diet changes and over-the-counter products are a reason to see the GP.

• Red flags need prompt review, whatever you have tried: bleeding from the back passage, unexplained weight loss, a lump in the abdomen, new bowel change at older ages, or waking at night with symptoms.

Taken by mouth, peppermint oil can cause heartburn, nausea, abdominal pain and dry mouth. Enteric-coated capsules make heartburn less likely, which is a reason not to open capsules or swap to uncoated oil. People with troublesome reflux or a hiatus hernia often find peppermint makes symptoms worse, because menthol relaxes the muscle at the bottom of the gullet.

Applied to the skin, peppermint oil can cause rashes, so it should be diluted and tried on a small area first. Tension headache is another possible use, with limited evidence that skin application might help.

For ordinary indigestion, research found benefit only for combination products containing peppermint with caraway oil, and peppermint oil alone might worsen symptoms. Inhaled peppermint oil showed particular promise for nausea and vomiting from chemotherapy, though this is a supportive measure to discuss with the oncology team rather than a treatment. Applied topically, it may soothe breastfeeding discomfort such as pain and cracked skin, but any product used on the breast needs to be washed off before feeding.

Menthol must not be inhaled by, or applied to the face of, a baby or young child, because it may cause breathing difficulties. That includes vapour rubs and aromatherapy diffusers near infants. Peppermint oil capsules are not a children's treatment, and the NHS does not recommend herbal medicines for children given the lack of safety information.

Pregnancy and breastfeeding are further reasons to check with a pharmacist or midwife first. The NHS advises checking before combining a herbal medicine with prescribed medicines, and interactions can occur, so mention it at any medicines review.

Peppermint oil capsules are available both as licensed or registered products and as food supplements. A registered product shows a THR mark and number, meaning the MHRA has assessed safety, quality and patient information. The MHRA has pointed out that most herbal medicines on the market are unlicensed and uneven in quality, so a clearly labelled, registered product is the safer choice.