Food protein-induced allergic colitis in babies: what parents should know

In some babies the immune system reacts to a protein in food and the lining of the lower bowel becomes inflamed. This is usually described as food protein-induced allergic colitis or allergic proctocolitis, and the commonest trigger is cow's milk protein. UK guidance generally discusses it under cow's milk allergy, which NICE CKS describe as a reproducible immune-mediated allergic response to one or more proteins in cow's milk.

NICE CKS divide cow's milk allergy by the way the immune system reacts. IgE-mediated reactions produce immediate symptoms that may affect several organ systems. Non-IgE-mediated reactions are delayed, usually appearing between 2 and 72 hours after ingestion, and often involve the gut and skin. Allergy UK says the non-IgE type is the most common type of cow's milk allergy. Allergic colitis belongs to this delayed group.

It is not the same as lactose intolerance. Allergy UK explains that cow's milk allergy is a reaction to the proteins casein and whey, whereas lactose intolerance involves the sugar in milk, and that management of the two is very different.

NICE guideline CG116 on food allergy in children lists the signs of non-IgE-mediated allergy affecting the gut. CKS adds that a diagnosis should be suspected if there are one or more symptoms that may be treatment-resistant.

• Loose or frequent stools, and diarrhoea.

• Blood and/or mucus in the stools.

• Gastro-oesophageal reflux, vomiting and abdominal discomfort or colicky pain.

• Constipation, or redness around the bottom (perianal redness).

• Food refusal or aversion, and infantile colic.

• Atopic eczema or other skin changes such as itching and redness.

• In more severe cases, pallor, tiredness or faltering growth.

Allergy UK says that if you suspect your child has cow's milk allergy you should not delay seeking advice from your GP or health visitor. Any blood in a baby's stool should be mentioned to a health professional rather than waiting to see if it settles. NICE CKS advise considering referral to a specialist allergy clinic for suspected non-IgE-mediated allergy if there is faltering growth, one or more severe reactions, or significant atopic eczema with multiple or cross-reactive food allergies.

Some reactions are emergencies. NICE CKS say that if there are systemic symptoms or suspected anaphylaxis an immediate ambulance transfer to A&E should be arranged, and the NHS says anaphylaxis starts quickly and can cause breathing problems, a swollen throat or tongue, or a raised itchy rash, and is a medical emergency needing urgent treatment: call 999.

Delayed symptoms can also have other causes. Allergy UK points out that symptoms such as eczema, colic, reflux and diarrhoea are common in infants and milk allergy is only one of a number of possible causes, so a GP or health visitor will take an allergy-focused history before drawing conclusions.

NICE CKS recommend asking about symptoms, the timing in relation to milk exposure, reproducibility of symptoms and any other allergic conditions, and examining nutritional status. For suspected non-IgE-mediated allergy, skin prick and blood tests are not the route: Allergy UK says they are not helpful and that the diagnosis is confirmed or excluded by a trial elimination of all cow's milk protein, either from the baby's diet if formula-fed or from the mother's diet if exclusively breastfed.

NICE CKS advise a trial elimination of all cow's milk from the mother's or infant's diet for 2 to 4 weeks, followed by a home reintroduction of cow's milk to confirm the diagnosis if there is a clear improvement. Allergy UK describes a trial of up to six weeks for a breastfeeding mother. This is done with the guidance of your GP, health visitor or dietitian rather than as a home experiment.

If cow's milk allergy is confirmed, the baby avoids cow's milk protein. For a formula-fed baby, Allergy UK says a special low-allergy (hypoallergenic) formula is prescribed: extensively hydrolysed formulas contain cow's milk protein broken into smaller pieces and most infants tolerate them, and an amino acid formula is used if symptoms persist. It notes that goat and sheep milk are not suitable alternatives, and that the baby's poo may change colour (dark green) and become less frequent when changing formula, which is normal.

For a breastfed baby, Allergy UK says the mother is advised to avoid cow's milk and dairy products while continuing to breastfeed. NICE CKS advise a cow's milk-free diet until the child is 9 to 12 months old and for at least 6 months if non-IgE-mediated allergy is confirmed, with referral to a paediatric dietitian to monitor growth and nutrition. The NHS says that babies with a cow's milk allergy who are not being breastfed may need special formula and to talk to your GP about what type to give.

The outlook is generally good. Allergy UK says most children grow out of cow's milk allergy in early childhood and NICE CKS say non-IgE-mediated allergy tends to resolve faster than IgE-mediated allergy. After the milk-free period, NICE CKS advise a home reintroduction of cow's milk, using a milk ladder, if there are no contraindications, to assess whether tolerance has been acquired.

Allergy UK describes the milk ladder as a step-by-step approach, starting with baked milk, such as in a biscuit, then cooked milk and finally uncooked milk. Reintroduction should be discussed with your GP, dietitian or allergy specialist first. The NHS adds that lots of children outgrow their allergies to milk or eggs, though some allergies can be lifelong.

The NHS recommends introducing allergenic foods one at a time from around 6 months, and says that if your baby already has a diagnosed food allergy or eczema, or there is a family history of allergy, you may need to be particularly careful and should talk to your GP or health visitor first. Read food labels carefully if your child has a food allergy and avoid foods if you are not sure whether they contain the food. Allergy UK offers factsheets on milk-free diets and the milk ladder, and its helpline can help signpost clinics.