Feature Review:

The Allergy Epidemic: A Look At The Facts

Vincent St Aubyn Crump FRACP, FRCP (UK) – 1 September, 2009

Introduction

Over the last 20 years there have been numerous reports in the media on the “Childhood Allergy Epidemic” worldwide, but specifically in developed countries, like New Zealand, Australia and the UK. There have also been an increasing number of stories on increasing asthma rates, increasing food allergy and anaphylaxis, &ldquo:the peanut allergy epidemic”, and talks of “banning peanut from schools”. There have also been recent media reports – mainly overseas – of children dying from peanut anaphylaxis. There is no doubt that, this increased media attention has led to an increased allergy awareness, and because there is an apparent “epidemic” of a disease that has potential life-threatening consequences for children, there is undoubtedly some amount of “hype”, and some sceptics might even say “parental hysteria”.

There are also sceptics who claim that “the food allergy epidemic is due to inconsistencies in the diagnosis of food allergy and in the definition of the cases and defects in the methods of some of the studies”. There is some truth to all of these criticisms. However, is there enough scientific evidence to justify an “Allergy Epidemic”? This paper will try to answer these questions in the form of an overview of the increasing prevalence of allergic diseases in New Zealand & in other developed countries, and will also look at the possible causes for this rapid increase.

Definitions in Epidemiology relevant to the Allergy Epidemic

• Epidemiology is the study in a population of the correlation between diseases, and the factors that regulate the appearance, spread (diffusion) and outcome of these diseases in human population
• An epidemic occurs when new cases of a certain disease occurs in a given human population, during a given period, substantially exceeds what is “expected” based on recent experience.
• Cohort is a set of people in a population sharing a common attribute e.g. age or ethnicity.
• Hypothesis is a theory that is held to be true and seems like it might be true until it is confirmed or proven wrong by empirical testing or evidence. In other words, an assumption or a mere guess.
• Incidence of a disease is the frequency, that is, the number of new cases of a particular disease in a defined population, identified during a given time. (usually 12 months, or the previous year, and usually referred to as annual prevalence)
• Prevalence of a disease is the total number of cases of a disease in a given population at a specific period of time or the percentage of the population that is affected with a particular disease at a given time.

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