Gastroenteritis in Babies and Children Under 5 Years

Gastroenteritis in Babies and Children Under 5 Years

Dietary Advice

Those of you who follow me on Instagram may be aware that Raffy had a horrible case of gastroenteritis whilst we were on holiday in June. As a result, we went to see a GP in Mallorca at a hospital who did some tests, checked him over and gave us some advice – including around his diet.

I shared all this on Instagram and as a result, got LOTS of questions from parents. Even now I get lots of people asking me about gastroenteritis and how to deal with it.

It’s important for me to be clear that I’m not a dietitian, which means I don’t have medical/clinical background as I specialise in public health nutrition.

Therefore, I went with advice I was given by the GP and I’d recommend that anyone in this situation checks with their GP first, at all times.

However, I also wanted to provide some context and information on my blog too, to help people understand dietary recommendations for any babies who have gastroenteritis.

Whilst I was away I had some great support from both The GP Mum and the guys below (paediatric Dietitians of Chichester), who helped me put this blog together based on dietary recommendations for gastroenteritis.

If you haven’t read my blog by Stephanie Patel –The GP mum, check that out first, as it goes over “what’s normal” when it comes to baby poo, as well as information on constipation and diarrhoea.

What is gastroenteritis?

Stools of children under the age of 5 vary greatly in terms of both consistency and frequency. Parents & carers will get to know their child’s normal bowel habits, what is normal for one child may not be for another. Diarrhoea is generally regarded as the passage of frequent, loose or watery stools. Diarrhoea in young children is often caused by an infection in the gut, known as gastroenteritis. It usually results in loose or watery stools (for those of you familiar with the Heaton stool chart, type 6 &7) and sometimes vomiting. 

What to do if your child has gastroenteritis?

Most children with gastroenteritis get better quickly without specific treatment and can be looked after at home safely. However, severe diarrhoea and vomiting can lead to dehydration which is when the body doesn’t have enough water or the right balance of salts. Dehydration is more likely to occur in young babies, typically under 6 months and in children who haven’t been able to drink enough during their illness. Children with dehydration will often feel, look and behave unwell. It can become serious so it is essential that if a child’s diarrhoea persist or if you become concerned in any way you call your GP immediately. The GP will often ask you a series of questions over the telephone to assess whether dehydration is likely. Prompt action can then be taken.

It is difficult to generalise when talking about gastroenteritis as the diarrhoea and vomiting can vary from child to child. However, the aim of treatment is primarily to prevent dehydration whilst maintaining adequate nutrition. Below is some guidance of how gastroenteritis can be managed in children under 5 years1.

  1. If your child has gastroenteritis but is NOT dehydrated:
  • Continue breastfeeding and other milk feeds as normal.
  • Offer frequent drinks
  • Do not give fruit juice or fizzy drinks as they can make the diarrhoea worse.
  • The GP or health visitor may suggest also offering oral rehydration solution (ORS) as a drink in small frequent amounts.
  1. If your child has gastroenteritis and IS dehydrated (after an assessment from your GP or paediatrician):
  • Offer oral rehydration solution as a drink in small frequent amounts over a period of about 4 hours.
  • Breast fed infants can have ORS in addition to breast milk if dehydrated.
  • Do not give any other drinks such as cow’s milk formula or cow’s milk unless your GP or paediatrician has told you to.
  • If commercially prepared ORS is not immediately available use cooled, boiled water. If you are abroad on holiday use cooled, boiled, bottled water.
  • After 4 hours reintroduce your child’s normal formula milk or cow’s milk.
  • Do not offer solid food until rehydrated.

Oral rehydration solution, such as Dioralyte, is a solution made up from a powder. It comes in sachets and can be bought in pharmacies and large supermarkets. It is made up of water, salt and sugar in specific amounts. Follow the instructions on the packet for preparing it. You should prepare it using the water your child usually drinks depending on their age. For children under 6 months of age this is boiled, cooled water. If the ORS causes your child to vomit or they will not drink it then call your GP. If your GP is not available then contact your out of hours GP service.

Stool frequency may increase when milk or solids are reintroduced. Don’t panic. This should not require milk feeds to be stopped again unless vomiting or dehydration occurs. ORS can be offered with each loose stool. In some children diarrhoea may persist. Diarrhoea that persists for longer than 7 days after gastroenteritis may be caused by secondary (often called transient or temporary) lactose intolerance (this is what I believe Raffy had!).

What is lactose intolerance?

Lactose intolerance is a digestive problem where the body is unable to digest lactose, the sugar mainly found in milk and dairy products. Lactose is digested by the enzyme lactase into simple sugars and absorbed into the bloodstream. The enzyme is found in the lining of the small intestines. When there is a deficiency or lack of lactase, lactose stays in the digestive system where it is fermented by bacteria. This results in the production of short chain fatty acids, lactic acid, methane, carbon dioxide and hydrogen. Symptoms such as flatulence, loose stools, diarrhoea, bloated stomach and stomach cramps can be experienced. Depending on the underlying reason why the body does not produce enough lactase, lactose intolerance may be transient (temporary) or permanent.

How can we develop secondary lactose intolerance?

There are a number of underlying causes of lactose intolerance. Secondary lactose intolerance can result from damage to the lining and the cells of the intestine. The damage can be caused by gastroenteritis such as rotavirus.

The damaged cells lining the intestine will quickly be replaced with new ones but they are often lactase deficient. This will result in lactose not being digested in the small intestine but pass into the colon where it may cause the subsequent symptoms as described above such as loose stools and diarrhoea. Infants who develop secondary lactose intolerance due to gastroenteritis should recover 6-8 weeks post infection. 

How do we treat secondary lactose intolerance?

Secondary lactose intolerance is treated by eliminating lactose from the diet. Lactose is found mainly in cow, goat & sheep milk and their products such as cream, cheese & yogurts. Other foods such as bread, breakfast cereal, biscuits & sauces may contain smaller amounts of lactose. It is therefore necessary to check food labels carefully. The word ‘lactose’ may not necessarily be listed separately on a food ingredients list and so food with milk and dairy products added may need to be avoided. The amount of lactose in dairy foods can varying widely so some children will be able to tolerate some foods more than others. Children with secondary lactose intolerance rarely need to follow the lactose free diet strictly but can tolerate small amounts in food. If your child cannot tolerate any lactose in the diet then ask your GP to refer you to a paediatric dietitian for assessment & help.

Let’s firstly consider infants under 12 months of age who will still be having a significant amount of breastmilk or breastmilk substitute (formula milk). Infants who are breastfed should continue to be so. Breastmilk contains lactose. Mum can cut down on her dairy intake if it helps the infant’s symptoms but it will not completely eliminate lactose from the breastmilk. If the infant is still experiencing symptoms on breastmilk then consult the GP who may suggest lactase substitute drops for the infant.

For infants who have a breastmilk substitute, symptoms should resolve when cow’s milk formula is stopped and replaced with a lactose free formula. In the UK, the lactose-free formula milks are:

  • Aptamil Lactose Free (Danone)
  • SMA LF (Nestlé)
  • Enfamil O-Lac (Mead Johnson)

If the child is also having solid food then this may also need to be lactose free as discussed above.

For infants who develop secondary lactose intolerance after their first birthday and are already drinking cow’s milk, symptoms should resolve when cow’s milk is stopped and replaced with an age appropriate, fortified milk alternative. Suitable options are:

  • Lactose free cow’s milk
  • Soya milk
  • Oat milk
  • Coconut milk
  • Pea milk
  • Nut milk

Ideally milk alternatives should be fortified with calcium & iodine (and B12 if following a vegetarian diet). Read the packaging carefully as some organic milk alternatives are not fortified. A lactose free diet may also be needed as discussed for infants under 1 year of age.

There is an enormous range of dairy free foods available in our shops and supermarkets. It is beyond the scope of this blog to highlight and discuss them all but follow us on Instagram for further suggestions.

Reintroducing dairy after secondary lactose intolerance.

It shouldn’t be long before milk and dairy products can be eaten again. To begin with offer small amounts of milk in foods such as milk in bread or breakfast cereal. Then start to offer dairy products such as a small amount of cheese. Yogurts, crème fraiche and fromage frais can then be given, increasing the quantity and frequency every few days. Finally reintroduce cow’s milk formula or milk into the diet. Hopefully a normal diet will be restored within a few weeks.

If loose stools persist when reintroducing milk and dairy products please consult your GP.

Written by

Dr Penny Barnard PhD RD Cert Allergy MBDA

Paediatric dietitian

On behalf of


1.NICE (2009) Diarrhoea and vomiting caused by gastroenteritis in the under 5s: diagnosis and management. NICE guideline CG84.  Accessed online: (August 2019).

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