I have written about food allergies before but the British Medical Journal published a clinical review on how to manage cows’ milk allergy in children in September of last year.
[Ludman S, Shah N, Fox AT. Managing cows’ milk allergy in children. BMJ 2013; 347: 28-32.]
This is a very useful paper because despite the NICE guidance on how to manage food allergies in children that was published in 2011, we still see a lot of mis-managed cases or children on all sorts of exclusion diets often presenting with malnutrition in one form or another.
So what does it tell us?
I think the most important points is to point out that even though cows’ milk allergy (CMP) can affect all ages, it is most prevalent in infancy, where it presents in the first few months of life and is one of the most common food allergies.
We also know atopic dermatitis or eczema is a risk factor for developing a food allergy and the earlier the eczema starts and the more severe it is, the higher the risk of developing a food allergy. Also a family history of atopy (eczema, asthma, hayfever) is a risk factor for developing food allergies.
[Hill DJ, Hosking CS. Food allergy and atopic dermatitis in infancy: an epidemiologic study. Pediatr Allergy Immunol 2004; 15: 421-7.]
How can you tell if someone has a CMP allergy?
There are 2 main types of allergic reaction, so called immediate and delayed. The difference is due to the antibodies or cellular reaction that is generated. They are called:
- Immediate or IgE-mediated hypersensitivity or
- Delayed or T-cell mediated hypersensitivity.
CMP allergy can give rise to both of these reactions.
What do they look like?
Immediate/IgE-mediated hypersensitivity
This usually can be seen within minutes, but no longer than 2 hours, of eating the food. There may be lip or tongue swelling, itching within the mouth, runny nose, hives or wheals around the face or body or even wheezing and features of anaphylaxis or collapse.
Delayed/T-cell mediated hypersensitivity
These are less easy to pinpoint, especially if dairy products are regularly eaten. Symptoms can be non-specific but commonly include reflux, colic or persistent crying, diarrhoea, constipation, food aversion, worsening of eczema and itch.
What should I do if I am worried my child has an allergy to CMP?
It is important that the health professional that you see takes an allergy focused history. The tests (skin prick tests and blood tests for specific IgE levels to foods) only confirm a clinical suspicion and are not indicative of a food allergy on their own. Skin prick tests should only be performed in centres that have the facilities to deal with an anaphylactic reaction as 0.12% of patients having skin prick tests will develop some sort of reaction.
I’ve had my child or myself allergy tested on the high street!
Alternative testing such as Vega testing, kinesiology, hair analysis or serum IgG testing are all not supported by NICE and there is no evidence to support the use of these investigations.
[NICE guideline 116: Assessment and diagnosis of food allergy in young children and young people in a community setting. (www.nice.org.uk/nicemedia/live/13348/53214/53214.pdf)]
My child has had IgE blood tests in the past. These are NICE recommended tests, so surely that’s proof my child has a food allergy?
Only if the tests were requested on the basis of an allergy focused history. Taking a blood test to see if there are IgE antibodies to, for example, peanuts will only show if there are IgE antibodies to peanuts. If your child has been eating all manner of nuts satisfactorily for some time, the presence of IgE antibodies to peanuts in their blood doesn’t necessarily mean they have a peanut allergy.
If someone had had wheezing and hives after eating chicken satay (made with peanuts) and their IgE blood test to peanuts was raised then that would be more indicative of a peanut allergy.
My blood test levels were in the “anaphylactic” range!
One patient told me this. On further probing, he had eaten a curry and developed a red rash around the mouth. An IgE blood test to peanuts had been requested and the level was raised. He had been counselled that the level was “anaphylactic”, he should avoid all nuts for life and carry two adrenaline autoinjectors around with himself for life.
A higher IgE concentration or a large wheal diameter on a skin prick test does not relate to the severity of the clinical response to exposure to the food. It just gives a higher probability of clinical allergy. This patient should have had a skin prick test to back up the blood test and possibly also an oral food challenge to see if he really did react to peanuts.
What is an oral food challenge?
These are undertaken if the allergy tests fail to confirm the history. The simplest and most widely practiced food challenge is an open oral food challenge. These should be performed in a unit with resuscitation facilities such as an allergy clinic or hospital day case unit.
My GP hasn’t referred my child for a food challenge, they’ve told me to exclude dairy from their diet!
A strict elimination diet is really the only way to diagnose a delayed-type hypersensitivity reaction to CMP as the skin prick tests and the IgE blood tests do not test for this type of food allergy.
If symptoms don’t improve within 2 to 8 weeks then CMP allergy is probably not responsible and dairy should be reintroduced. Improvement on exclusion of the food followed by recurrence of symptoms on reintroduction is strongly indicative of a delayed-type reaction.
[Koletzko S, Niggeman B, Arato A et al. Diagnostic approach and management of cows’ milk protein allergy in infants and children: ESPGHAN GI committee practical guidelines. J Pediatr Gastroenterol Nutr 2012; 55: 221-9.]
How is CMP allergy managed?
If CMP allergy is proven, exclusion is the only management. First line treatment is with an extensively hydrolysed formula and if symptoms do not resolve with that after 8 weeks, then an amino acid formula should be used.
Dietetic support is essential as children with food allergies can often become malnourished or obese and the family need counselling on how to avoid the food and how to manage any reactions from inadvertently eating the food.
Soya milks should not be used in children under the age of 6 months (as they contain isoflavin, a weak oestrogen) and there is cross-reactivity between CMP and soya allergy. Other mammalian milks such as goat, mare or sheep are not recommended, also because of high species cross-reactivity.
What is the long term outlook?
Around 60% of children grow out of their CMP allergy by 5 years of age. Severe reactions, worry over multiple food allergies, faltering growth or children with concomitant asthma should all be referred to see a paediatric allergist.
Regards,
Sandy
Dr Sandy Flann, Consultant Dermatologist
