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Allergic Colitis


Otherwise well appearing infants presenting with blood and mucus in the stool, hives, vomiting, and diarrhoea or flare up of atopic dermatitis after introduction of cow’s milk when they are aged approximately 3 weeks to 3 months (can be 0-10 months). Most commonly these children are well, it is a benign and self-limiting disorder and they can be discharged with advice. However, massive rectal bleeding from allergic colitis has been reported and the management of this is not reported here.

Note that allergy is probably over diagnosed in infants presenting with bloody stools and aetiology is often uncertain and remains as such.

Differential Diagnosis

  • Swallowed maternal blood from cracked nipples (most common).

  • Infectious colitis.

  • Necrotising Enterocolitis (NEC).

  • Anal fissure.

  • Hirschsprungs disease – 80% children present in first year of life often with delayed passage meconium or constipation. 25% present with enterocolitis causing severe watery +/- bloody diarrhoea, abdo distension, colonic perforation and shock.


Usually a well infant with normal growth pattern.


  • Stool culture – ensure not infectious colitis.

  • Consider a FBC – look for eosinophilia.


  • If the child is well with less than 6 bloody stools/day the child can be discharged with dietary advice - can trial dairy and soy avoidance in baby and maternal (if breast feeding) diet and GP follow up. 50% of children with true cows milk allergy will resolve within 2 years and 80% by 3-4 years after diagnosis. See Figures 1 and 2 in Vandenplas et al. for diagnosis and management of formula and breast fed infants.

  • If there are more than 6 bloody stools/day or the diarrhoea is persistent >7 days or the child is unwell at presentation then referral to gastroenterologist for scope required.

  • If the child is unwell they need to be admitted under the paediatrician (with paediatric gastroenterology if possible).

Further References and Resources

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