In light of Allergy Awareness Week 2018 (23rd April – 29th April), here I review the latest potential food allergy prevention strategies which take a nutritional approach in the early years of life. I also discuss the concept of immunotherapy as a treatment method for those with established food allergies.
The past two decades has seen a dramatic increase in allergy prevalence, particularly in infants and children. UK hospital admissions for children with food allergies have increased by 700% since 1990, with 5-8% of children having a proven food allergy. Moreover, recent evidence indicates food allergies are becoming more common in adolescents and young adults too. There is clearly a great need for both effective allergy prevention strategies and methods to improve the lives of those affected by food allergies.
Nutritional intervention as a preventative measure to combat food allergy prevalence has gained significant attention in recent times. Whereas the previous approach was to avoid potential food allergens in infants, such attitudes have changed, and here I will discuss some of the most prominent new approaches to food allergy prevention.
Hygiene hypothesis, gut bacteria and probiotics
In modern life humans are too clean – avoiding any possible exposure to microbes. This means the immune system isn’t practiced in identifying legitimate threats, and overcompensates in the form of allergy as a result. This key theory for the causation of allergies is called the ‘hygiene hypothesis’. Studies have shown that growing up in a rural farm environment significantly reduces the risk of allergic disease in children. Furthermore, there are dramatic differences in the gut bacteria profiles between allergic and nonallergic infants/children. Increasing infant gut bacteria diversity could help prevent allergy onset, with probiotic supplementation indicated to reduce the risk of atopic dermatitis in infants. More studies are needed to properly determine the effectiveness of probiotics in preventing allergy onset.
Early allergen introduction in the infant diet
It was previously recommended that the introduction of common food allergens to the infant diet should be delayed (e.g. cow’s milk after 12 months, peanut after 3 years). The latest approach suggests that allergen tolerance may actually be achieved by introducing food allergens between 4-6 months when weaning solids, and delayed avoidance in introducing allergens may increase the risk of food allergy. This concept was supported by the Australian HealthNuts Study, which found that introducing egg after 12 months of age significantly increased the risk of developing egg allergy. Furthermore, early introduction of peanut from 4 months was shown by the LEAP (Learning Early about Peanut) study to have a protective effect against peanut allergy in high-risk infants. The logistics of introducing such allergens are yet to be optimised, and as such more work is required in this area before the WHO would recommend early allergen introduction.
Low vitamin D levels have been indicated to increase the risk of developing a food allergy, with a previous study demonstrating this effect in the case of egg and/or peanut allergy. Similarly, food allergy and eczema have been observed to be more prevalent in areas with less sun exposure, following a geographical north-south gradient. Other investigations have indicated that abnormally high doses of vitamin D also increase the risk of food allergy in infants. As it is suggested that both insufficiency and over-supplementation of vitamin D act as risk factors for allergy, a current trial (e.g. VITALITY) to assess the role of moderate supplementation in preventing allergy is ongoing. Nevertheless, vitamin D plays a prominent role in the risk of developing a food allergy.
Treatment – food allergen immunotherapy
The only current established treatment method for those with a food allergy is simply elimination of the allergen from the diet. However, allergic individuals are still at risk of consuming poorly labelled products or accidental food preparation mistakes, and are consequently in danger of fatal inadvertent reactions such as anaphylaxis. The concept of immunotherapy has been introduced to theoretically improve the quality of life for those suffering with food allergy. Taking oral immunotherapy as an example, a food allergen would be introduced into a patient’s diet at a very low dose before increasing this dose in a stepwise fashion under medical supervision until a maintenance dose was achieved. The patient would hypothetically gain a state of desensitisation whereby they would not react to the allergen with an immune response. The effectiveness of oral immunotherapy was tested in a study that saw 79% of peanut-allergic individuals successfully desensitised to peanut protein (443 mg). The remaining 21% had initial allergic reactions that were too severe to continue, but methods are being explored to reduce the side effects when updosing with the allergen. This includes combining oral immunotherapy with biological compounds that reduce the sensitivity to allergens. Further research is required in this area to determine the best method for maintaining the desensitised state, which for some may not be long-lasting. Regardless, this concept has the potential to improve the lives of those that suffer severe reactions to minimal amounts of allergen.
Recent research has provided promising prevention and treatment strategies that could stop the growing prevalence of food allergy continuing. The next logical steps should involve establishing the appropriate delivery of these strategies in the healthcare environment.