Making sense of allergies – various thoughts from the publication

Adam Fox, Consultant Paediatric Allergist

“The influence of early use of antibiotics in infants on their microbiome and subsequent impact on the risk of allergy remains unclear. What is clear, however, is that babies are very vulnerable to bacterial infections and these must always be taken very seriously. If there is a clinical need for antibiotics, they should be used and the possible theoretical impact on allergies should not influence this decision.”

studies, carried out in a number of countries, have found that children
who grow up on farms have lower levels of hay fever, asthma and other
allergies. This, and other work, has shown that exposure to environments
rich in microbes during childhood and whilst in the womb may have beneficial effects[25,26]. Some of this work has linked raw milk to reduced allergies, but the risks of drinking it (it could contain harmful bacteria Campylobacter, E coli O157, or Salmonella) are likely to outweigh any possible benefits.

The Old Friends Mechanism is the predominant theory among allergy specialists. However misuse of the term ‘hygiene’ has persisted and has led people to believe that reducing levels of hygiene is a good idea, such as hand washing dishes instead of using a dishwasher. This can transmit disease. Instead, the advice from more developed research and understanding is to continue targeted hygiene practices such as hand washing, food safety, and toilet hygiene, while encouraging more everyday interactions with our environment, including getting outside and getting dirty

Sally Bloomfield, Honorary Professor, London School of Hygiene and Tropical Medicine

“With people now spending up to 80% of their time indoors, the fundamental question now is ‘how can we develop an approach to hygiene which protects us against infectious diseases, but also reconnects us with the necessary microbial exposures required for the health of our immune system?’”


Some people have a genetic tendency towards developing allergies. This is called atopy and is why being allergic can run in families. However, being atopic does not guarantee an allergy will develop, it just means it is more likely. Atopic family members frequently have different kinds of allergies to each other. Identical twins are more likely to have the same allergies[28]. Genetic factors have a role but can’t help us predict exactly who will develop an allergy.

Parents worry about when to introduce foods that might cause allergic reactions into children’s diets and there are no overarching rules to guide them. Researchers don’t have a good idea why early exposure to some allergens can reduce rates of those allergies.

Researchers found that peanut allergies are more common in the UK than in a genetically similar population in Israel, where peanut-containing foods are eaten at an earlier age[29]. In 2015, the results of a large study – Learning Early About Peanut Allergy (LEAP)[30] – showed that exposing young children who were at high risk of developing allergy to foods containing peanuts reduced the incidence of peanut allergy to just 3.2%, down from 17.2% in children who had not been exposed.


Research so far has tended to focus on serious allergies especially peanut allergies. New avenues of research focusing more on population level factors have started to be explored including a possible link between vitamin D deficiency and risk of anaphylaxis[32], changes in the climate of the Northern Hemisphere (leading to longer pollen seasons and changing distributions of plants), socioeconomic factors and stress. All of these can interact with our genes and change our microbial environment.


Ambivalence about the benefits of modern living seems quite strongly focused on the need to reduce ‘man-made chemicals’ and the desire for a more ‘natural’ life or diet. This has led to a demand for synthetic substances in products to be replaced by ‘natural alternatives’ made from animal and plant extracts. However, this actually increases the risk of exposure to allergens. For example, replacing synthetic compounds in soap with ‘natural’ wheat has led to more allergic reactions in people allergic to wheat.