Acute diarrhoea is one of the most common reasons for self-medicating in the UK. Most cases are viral, short-lived and managed at home — but knowing how to manage it correctly, particularly regarding dehydration, can prevent complications, especially in the very young and elderly.

Types and Causes of Diarrhoea

Acute infectious diarrhoea — the most common type. Caused by viruses (norovirus, rotavirus), bacteria (Campylobacter, Salmonella, E. coli, Clostridioides difficile) or parasites (Giardia). Viral gastroenteritis typically self-resolves in 1–3 days. Bacterial causes may require antibiotic treatment. Traveller’s diarrhoea — affects 20–50% of international travellers; usually caused by E. coli in unfamiliar food or water. Antibiotic-associated diarrhoea — disruption of gut flora during or after antibiotic courses. Functional diarrhoea — IBS-D, stress-related. Osmotic diarrhoea — excessive consumption of sorbitol (sugar-free products), lactose intolerance, or malabsorption.

The Priority: Preventing Dehydration

Diarrhoea causes rapid fluid and electrolyte losses. The danger is not the stool frequency itself but the dehydration it causes. For most healthy adults, drinking sufficient water is adequate. However, oral rehydration solutions (ORS) such as Dioralyte contain the optimal balance of glucose and electrolytes (sodium, potassium, chloride) in proportions that match fluid losses and maximise absorption via the sodium-glucose co-transport mechanism. ORS is essential for: children under 5, adults over 65, people with diabetes, those with signs of moderate dehydration (dry mouth, decreased urination, dizziness), and anyone with significant vomiting alongside diarrhoea. Avoid sugary drinks and fruit juice — the high osmolarity worsens diarrhoea.

OTC Medicines for Diarrhoea

Loperamide (Imodium) — the most effective OTC antidiarrhoeal. Acts on opioid receptors in the gut wall, slowing bowel motility and increasing reabsorption of water and electrolytes. Provides significant symptomatic relief, allowing people to function normally. Not a cure — it treats the symptom while the underlying cause resolves. Do not use if: blood or mucus in stool, high fever, diarrhoea following antibiotic use (risk of C. diff), children under 12 without medical advice. Do not use if suspected inflammatory bowel disease flare.

Bismuth subsalicylate (not commonly available OTC in UK) has some antibacterial and antisecretory properties. Probiotics — evidence supports their use for shortening duration of acute infectious diarrhoea, particularly in children (Lactobacillus rhamnosus GG, Saccharomyces boulardii). Also useful for preventing and treating antibiotic-associated diarrhoea.

Dietary Approach During Recovery

The old BRAT diet (bananas, rice, apple sauce, toast) is no longer specifically recommended — eat whatever feels tolerable. Small, frequent, bland, low-fat meals. Avoid dairy, high-fibre foods, fatty foods, and alcohol until stools normalise. Gradually return to normal eating as symptoms improve.

When to See a Doctor

Seek medical attention if: diarrhoea lasts more than 48 hours in adults (24 hours in children under 2), blood or mucus in stool, fever above 38.5°C, signs of significant dehydration, recent foreign travel, recent antibiotic use, or diarrhoea in an immunocompromised person.

Browse Diarrhoea treatments at Huncoat Pharmacy. Related: Gut Health Guide, Stomach Health While Travelling.

At Huncoat Pharmacy: Pharmacy First, Browse diarrhoea treatments, Travel health service.