Irritable bowel syndrome (IBS) is the most common functional gastrointestinal condition in the UK, affecting approximately 1 in 5 people. It causes real, sometimes debilitating symptoms — yet it’s often dismissed or poorly treated. This guide is for those who want to understand and take control of their condition.

What Is IBS?

IBS is a functional disorder — meaning the gut looks normal on investigation, but doesn’t function normally. It is characterised by recurrent abdominal pain associated with changes in bowel habit (constipation, diarrhoea, or a mixture of both), often with bloating and excessive gas. IBS is now understood to involve dysregulation of the gut-brain axis, altered gut motility, visceral hypersensitivity (the gut’s pain sensors become over-reactive), microbiome imbalances, and sometimes post-infectious changes.

IBS Subtypes

IBS-C (constipation-predominant): hard, infrequent stools, straining, sensation of incomplete emptying. IBS-D (diarrhoea-predominant): loose, urgent stools, urgency, sometimes with incontinence. IBS-M (mixed): alternating between the two. IBS-U: unclassified. Subtype recognition matters because it guides treatment choices.

Common Triggers

IBS is highly individual — what triggers one person won’t affect another. Common themes include: FODMAPs (fermentable carbohydrates that draw water into the bowel and are fermented by bacteria — found in wheat, onion, garlic, dairy lactose, certain fruits), stress and anxiety (the gut-brain connection is remarkably direct in IBS), irregular meal timing, large meals, fatty foods, caffeine and alcohol, hormonal fluctuations (symptoms often worsen perimenstrually in women), and antibiotics.

The Low-FODMAP Diet

The best-evidenced dietary intervention for IBS, developed at Monash University in Australia. It involves a 6–8 week elimination phase (restricting high-FODMAP foods), followed by systematic reintroduction to identify personal triggers, and a long-term personalised diet. Around 70% of people with IBS experience significant symptom improvement. Ideally undertaken with dietitian support. The Monash FODMAP app (£) is an excellent tool for this process.

OTC Treatments for IBS

Antispasmodics — Buscopan (hyoscine butylbromide) and Colofac (mebeverine) are the standard OTC treatments for IBS abdominal pain and cramping. They relax smooth muscle in the gut wall, reducing spasm. Mebeverine has slightly stronger evidence; hyoscine acts more broadly. Take 20 minutes before meals for best effect.

For IBS-C: increase dietary fibre (introduce gradually to avoid worsening gas), consider a soluble fibre supplement such as ispaghula husk (Fybogel) — stir well and drink plenty of water. Low-dose polyethylene glycol (Movicol, Laxido) for short-term use.

For IBS-D: loperamide (Imodium) for short-term control of urgency. Avoid overuse — it does not address underlying causes.

Peppermint oil capsules (Colpermin, Mintec) — enteric-coated, so they release in the small intestine. Multiple trials support their use for IBS pain and bloating. A reasonable first-line option for mixed or pain-predominant IBS with minimal side effects.

Probiotics — evidence is modest but meaningful for some IBS subtypes. Bifidobacterium infantis 35624 (Alflorex) has the strongest RCT evidence for IBS specifically. Lactobacillus acidophilus-based probiotics may help IBS-D. Requires consistent use for 4–8 weeks to assess effect.

Browse IBS treatments at Huncoat Pharmacy. Related: Constipation Relief, Heartburn Guide.

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