Temporary allergy to Neocate: possible association with immunisation

Abstract

A 5-month-old baby exhibited an allergic reaction to Nutramigen 1 day after his third set of immunisations. The following day he had a similar reaction to Neocate, which was being used as an alternative to Nutramigen. One month later Neocate was slowly reintroduced back into the diet with no ill effects.

BACKGROUND

Neocate is generally thought to be the gold standard in the treatment of cow’s milk protein allergy and intolerance. Allergic reactions to Neocate are very rare. This case illustrates that allergic reactions to this amino acid based infant formula can occur and that this can be a temporary state. In future cases this type of clinical challenge might be tackled by judicious desensitisation. This temporary allergy to Neocate may have been causally associated with immunisation.

CASE PRESENTATION

Following ABO incompatibility in the neonatal period this boy made satisfactory progress regarding his growth and development. He was exclusively breast fed for the first 5 months of his life. His first two sets of immunisations were not associated with any significant problems. At 5 months he reacted within 15 min of his third set of immunisations. He became cold and clammy, with stridor and facial swelling. This led to admission to hospital where he was treated with antihistamines and nebulised Budesonide, with a favourable response. The next morning his mother asked whether she could have an alternative to breast milk for her child. Nutramigen was recommended in view of a positive family history of atopy and a sibling with severe cow’s milk allergy. Almost immediately on giving him Nutramigen he developed lip swelling, facial urticaria and erythema around both eyes. He was allowed home with advice to try Neocate outside the hospital on the following day. The subsequent reaction to Neocate was similar to that with Nutramigen and was successfully treated with an antihistamine.

INVESTIGATIONS

Investigations at the time of the original reaction showed an 8 mm positive skin test (weal) to SMA (UK cow’s milk formula) and negative skin tests to Nutramigen, Neocate and Rice Milk. The positive weal was 2 mm and negative control gave no reaction. The total IgE was 55 iu/ml. The RAST test to milk was grade 2 positive (equivalent to 0.7–3.5 IgE units) with negative RAST tests to wheat, soya and egg. At the age of 6 months he had a 5 mm positive skin test to Soya and a 2 mm positive test to Neocate. At 1 year of age the skin prick test to milk was 5 mm and negative to Soya.

TREATMENT

One month after the initial allergic reaction the infant was challenged in hospital to a small volume of Neocate. Over the next 4 weeks his mother gave him increasing volumes. By the age of 8 months he had established an acceptable total intake of 540 ml/day.

OUTCOME AND FOLLOW-UP

As a result of a negative skin test at the age of 1 year, Soya was introduced instead of Neocate with no difficulty.

DISCUSSION

Allergy to cow’s milk is a common clinical problem in infancy with up to 10% of infants affected. An amino acid based formula, such as Neocate, is often used in preference to Soya as a substitute because of concerns regarding possible cross-sensitisation to peanut and the theoretical risk of exposure to oestrogen-like compounds. Also, amino acid based preparations are thought to have minimal potential for causing an allergic reaction. Reports of immediate type 1 allergic reactions to Neocate are very rare.^1–3 A study of 20 children with proven cow’s milk allergy revealed no cases of positive skin prick tests to Neocate, which implied to the authors that there was no residual allergenicity in amino acid based formulae.⁴

Cross-contamination was thought to be unlikely in this case as the Nutramigen and Neocate were administered on separate days and were individually prepared. There was an association with a recent immunisation. While this might be considered coincidental it may represent a priming of the immune system following the immunisation reaction. An alternative explanation may be that a coincidental viral infection caused a non-specific increase in immediate type hypersensitivity. However, this seems a less likely explanation as the positive skin prick test to Neocate at the age of 6 months implies a specific IgE response. In addition there was no direct evidence of a viral illness at the time of the reactions to Nutramigen and Neocate. Residual Soybean proteins have been implicated as causing allergenicity in amino acid preparations;² this might offer a further explanation for the train of events in our case if the immunisation reaction was not a causal factor in the clinical picture. The timing of events might also have been entirely coincidental.

It is tempting to postulate that his mother desensitised her child to Neocate over a 1-month period. Meglio et al⁵ successfully desensitised 15 of 21 children with proven severe cow’s milk allergy over a 6-month period. This illustrates that desensitisation is possible, although not commonly undertaken in the UK. Based on our case of allergy to Neocate it may be worth challenging after a shorter period of avoidance than is usually practised in infants with cow’s milk allergy with this type of clinical scenario.

LEARNING POINTS

• Neocate allergy can occur.

• The allergy may only be temporary.

• Allergy to Neocate may not necessarily be indicated by a positive skin prick test.