Food Allergies in Children – Dr Adam Fox, Consultant Paediatric Allergist at Guy’s and St Thomas’ Hospitals
Part of the annual Nutrition and Health Live event – November 2013
“Something has changed over the last century,” said Dr Adam Fox, Consultant Paediatric Allergist at Guy’s and St Thomas’ Hospitals, opening his talk, Food Allergies in Children.
25% of adults have allergies; 40% of children. The rapid increase from rare disease (hay fever was virtually unknown at the end of the 19th century) to epidemic cannot be down to genetics, as relatively speaking the change is too sudden. However, the environmental factors remain unclear. Depressingly, the UK tops the international table of allergic disease, closely followed by New Zealand, Australia, Ireland and Canada. Given the disparate geography of these nations, it must be the cultural similarities that account for the allergy epidemic.
5% of children have genuine food allergy, but 33% of parents believe their child has a food allergy. Medical professionals, said Fox, are dealing with two epidemics: the real food allergy epidemic in children, and the far greater epidemic of parents believing that whatever is wrong with their child – skin problems, headaches, lethargy, behavioural problems – are down to food allergy when they are not.
Atopic children who present with eczema in infancy are more likely to develop food allergy, and later on asthma and rhinitis – a progression known as the allergic march. These allergic conditions influence one another in many ways:
* if you have eczema and egg allergy – then you have a 70-80% risk of asthma;
As the overlap between eczema and food allergy is considerable, it is the skin on which the research is focusing. Virtually all peanut- or egg-allergic children have significant eczema in their first year. Research shows that infants with mild eczema have a 10% chance of developing food allergy; those with severe eczema a 70% chance. The earlier the eczema, the greater the risk.
It is unusual to outgrow peanut allergy – only 20% of children manage it. Interestingly, 90% of children with peanut allergy react the first time they eat peanuts. Immunologically, said Fox, this makes no sense, as the immune system must have already been presented the peanut allergen (and subsequently become sensitised to it). Where and when is sensitisation taking place?
Previous speculation – that sensitisation may occur in utero, or during breastfeeding, if the mother consumed peanuts in either case – has since been disproven, leading to the withdrawal in 2009 of the previous cautious Department of Health recommendations to atopic mothers-to-be and mothers that they may want to consider avoiding peanut in pregnancy and during breastfeeding, and to avoid feeding peanuts to their children in the first three years of life.
Focus has shifted to eczema. The use of peanut-containing eczema skincare products (such as Oilatum, which formerly contained it) has been shown to be a significant risk factor, but even after the removal of peanut from most skincare preparations, peanut allergies continue. So there must be exposure to peanut protein via other means – other children handling peanut butter and touching the children, a parent who has eaten peanut butter kissing the child, inhalation of dust with peanut allergen in it, and so on. We know peanut allergen can ‘linger’ in the home, and be carried from room to room easily. Research has shown a tenfold increased likelihood of peanut allergy if there is a lot of peanut in the home environment.
Although nothing has replaced the old 2009 advice, more studies will hopefully address this. Possible prevention strategies include:
* aggressive early eczema treatment. If early and severe eczema is a significant risk factor, aggressive treatment at this stage may reduce risk of food allergies. Fox acknowledged it may be difficult to persuade mothers to put steroid cream on their young infants, however.
A common question, said Fox, was ‘Does it go away?’ It’s tricky to predict whether a food allergy may disappear, but those children more likely to outgrow them are those with lower IgE levels at diagnosis and milder initial eczema.