Incidence/prevalence

Overall, a quarter of the childhood population suffer from allergy of one type or another. The majority have mild symptoms such as mild hay fever. Up to 7% of all children have allergic reactions to foods but most reactions are mild. The majority of children will have begun to grow out of their food allergy before they start school. Egg (2.5% of the population), milk (2.5-3.8%) and peanut (2%) are the most common triggers of food allergy reactions in young children.

The prevalence of allergic disease, particularly the incidence of anaphylaxis has increased dramatically over the last 30 years. A UK study showed that rates of hospital admission for anaphylaxis increased from 6 admissions per year per million of population in 1990 to 41 admissions per year per million of population in 2000. There is evidence that rate of increase is tailing off and incidence of new allergy is stabilising at the new higher level. From population-based data, the incidence rate, where this is defined as the number of episodes of anaphylaxis that occur in a defined population over a given period of time, is estimated at between 80-210 episodes per million person-years. Incidence varies by age, gender, geography and socio-economic position.

The most common trigger for anaphylaxis in childhood is food (41-57%), followed by medicinal drugs (6%-34%). The most frequent food triggers in childhood are peanut and nuts, cows milk, hen eggs, fish and shellfish. Anaphylaxis due to other triggers such as insect venom or exercise is rare.

Around 1-2% of adults have diagnosed IgE mediated allergies that could result in anaphylaxis. Peanut, nut and fish allergies are the most common severe allergy in the adult population. A range of other allergies develop over time in older children and adults. Examples include allergies to fruits, drugs and insect venom. Consequently allergies in adults and older children are more diverse.