When a parent walks into a UK pharmacy with a vomiting or diarrhoeic child, the single most useful thing the counter can provide is an oral rehydration salts (ORS) sachet and a clear explanation of how and when to use it. The science behind ORS is simple — glucose and electrolytes in fixed ratios that the small intestine will absorb even when the gut is inflamed — and the NHS has promoted it as first-line for mild-to-moderate dehydration in children for decades.
But the pharmacy also has a filtering role. Most gastroenteritis resolves at home. A minority does not, and recognising that minority quickly is where the counter adds the most value.
What ORS actually is
UK-licensed ORS products (Dioralyte, Electrolade, pharmacy-own-brand sachets) are based on the World Health Organization reduced-osmolarity formulation. Each sachet, dissolved in a stated volume of water, provides a fixed concentration of sodium, potassium, chloride, citrate and glucose. The glucose-sodium co-transporter in the small intestine continues to work during viral gastroenteritis, which is why ORS is absorbed when plain water alone is less efficient.
NICE CG84 (the cornerstone UK guideline on diarrhoea and vomiting in children under 5) recommends ORS as the first intervention for children with clinical dehydration but without red flags, and increasingly for children at risk of dehydration — for example infants, children with more than five diarrhoeal stools in the past 24 hours, or those with two or more vomits.
How the pharmacy explains using it
The counter-level script is usually:
- Reconstitute exactly as directed — each brand specifies a volume of water per sachet. Under-diluting can cause dangerously high sodium; over-diluting reduces the therapeutic effect.
- Give small, frequent amounts. A teaspoon or 5 ml every 1–2 minutes is often easier to tolerate than larger volumes in a child who has just vomited.
- Aim for 50 ml per kg over 3–4 hours for clinical dehydration, plus replacement of ongoing losses. NICE CG84 sets this out explicitly.
- Carry on breastfeeding between ORS offers for infants. This is an important departure from older advice to "rest the gut".
- Avoid fruit juice, squash or fizzy drinks as the sole fluid during acute illness — sugar loads without the sodium can worsen osmotic diarrhoea.
- Once rehydrated, return to a normal diet — the old BRAT (bananas, rice, apples, toast) idea is not supported by current UK guidance.
Once-opened sachets made up in water should be used within 24 hours and kept refrigerated.
When ORS is the right answer
ORS is indicated for:
- Children with mild-to-moderate clinical dehydration from gastroenteritis
- Children at high risk of dehydration (frequent stools, multiple vomits, infants under 1)
- Children with reduced oral intake who are otherwise well
- Older children and adults with diarrhoea and vomiting
Red flags that override ORS and go straight to 111 or A&E
NICE CG84 and NHS patient information are consistent on when home management is not safe:
- Infant under 3 months with fever, vomiting or diarrhoea
- Signs of shock — pale, mottled, cold peripheries, unusually sleepy, weak pulse
- Reduced level of consciousness or unusual drowsiness
- Blood in stool (more than a trace streak)
- Bilious (green) vomiting
- Severe abdominal pain or localised tenderness
- Persistent vomiting preventing any fluid intake for more than a few hours
- No wet nappy for 6+ hours in an infant, or no urine passed in 8–12 hours in an older child
- Sunken eyes, sunken fontanelle, cold peripheries, prolonged capillary refill
- Underlying conditions — pre-existing serious illness, short bowel, ileostomy, recent abdominal surgery, immunocompromise
Parents need to know these plainly: the role of the pharmacy is to give ORS and the list.
Anti-diarrhoeals are not for young children
Loperamide and similar motility-slowing agents are not routinely recommended for children with acute diarrhoea in the UK. Loperamide is contraindicated under 12 in NICE CG84 and the BNFc. The NHS position is clear: rehydration, not bowel stopping, is the treatment.
See our loperamide guide for the over-12 and adult picture.
Probiotics
The evidence for specific probiotic strains reducing diarrhoea duration by a day or so in children is now reasonably solid, but NICE CG84 does not recommend them routinely for UK NHS care. Pharmacies may still stock and sell them; the counter should frame them as an adjunct, never a replacement for ORS.
Zinc
Zinc supplementation is a WHO-recommended adjunct in low- and middle-income countries where baseline zinc deficiency is common. It is not part of UK NICE guidance.
Summary for the counter
| Situation | What the pharmacy should do |
|---|---|
| Well child, loose stools, drinking normally | Reassurance; usual diet; ORS if losses pick up |
| Mild-moderate dehydration | ORS at 50 ml/kg over 3–4h + ongoing losses |
| Any red flag above | 111 or A&E — do not start ORS at the counter and send home |
| Infant under 3 months unwell | 111 or urgent GP, always |
| Child under 12 asking for loperamide | Decline; rehydration only |
ORS is cheap, widely stocked and one of the highest-value interventions a UK pharmacy can deliver. The harder skill is knowing when not to use it.
Sources
- NICE CG84 — Diarrhoea and vomiting in children under 5
- NICE CKS — Gastroenteritis
- NHS — Diarrhoea and vomiting
General information for UK pharmacy customers. If in doubt about a child's condition, contact NHS 111 or your GP rather than self-managing.