Understanding Food Allergy
Food allergy is a rapidly growing global health problem1. While rates of food allergy have increased most rapidly in developed countries, recent studies suggest that similar increases are occurring in developing regions alongside rapid economic growth2.
In people with food allergy, the immune system incorrectly recognizes the food allergen as potentially harmful, and produces IgE antibodies directed against the allergen. These IgE antibodies bind to receptors on the surface of specialised allergy effector cells, known as ‘mast cells’, which are present in the tissues of the skin, airways and intestine. When the food is eaten, food allergens enter the body and bind to the food-specific IgE antibodies on mast cells, causing the mast cells to release a variety of immune factors that cause the symptoms of an allergic reaction. Symptoms of an allergic reaction can range from mild itching and redness of the skin, hives, and gastrointestinal upset to life-threatening anaphylaxis, with noisy or difficulty breathing and fall in blood pressure.
The steps leading to an allergic reaction
The reasons why the immune system in people with food allergy incorrectly recognises food allergen(s) as harmful are not fully understood. Studies suggest that the circumstances in which the immune system first encounters the food allergen(s) might be important in determining whether there is a natural tolerance response or the development of food allergy. For example, if the first encounter between the immune system and food allergen(s) takes place in the healthy intestine, such as when a healthy person eats a food for the first time, specialised tolerance promoting cells that are abundant in the intestines instruct the immune system to develop a tolerance response to the food allergen(s). If on the other hand, the immune system first encounters food allergen(s) entering the body through inflamed skin, such as through skin that is affected by eczema, the wrong signal is delivered to the immune system resulting in an allergic response rather than a tolerance response.
There is currently no effective long-term treatment for food allergy. Patient management focuses on avoiding the food concerned, early initiation of appropriate emergency treatment of allergic reactions, particularly anaphylaxis, and in selected patients, provision of an adrenaline autoinjector. The constant vigilance required to avoid food allergens and the ever-present possibility of a serious allergic reaction lead to a significantly reduced quality of life.
It is estimated that around 1 in every 50 people in the US is allergic to peanut3, and every year about half suffer an allergic reaction due to accidental ingestion of peanut that is impossible to predict or prevent4. Fortunately, fatalities are rare, however accidental peanut exposure and the possibility of a potentially life-threatening reaction remain an ever-present cause of anxiety.
Peanut allergy is usually lifelong. It is the most common cause of life-threatening reactions (anaphylaxis)5 and the most common cause of death from food-induced anaphylaxis6-8. Children with peanut allergy report a significantly reduced quality of life worse than that of children with diabetes9.
- WAO White Book on Allergy 2013 Update – http://www.worldallergy.org/wao-white-book-on-allergy
- Loh W and Tang The Epidemiology of Food Allergy in the Global Context. Global Health, The Epidemiology of Allergy. Int. J. Environ. Res. Public Health 2018;15(9):2043
- Bunyavanich S, Rifas-Shiman SL, Platts-Mills TA, et al. Peanut allergy prevalence among school-age children in a US cohort not selected for any disease. J Allergy Clin Immunol. 2014 Sep; 134(3): 753–755
- Bock SA, Atkins FM. The natural history of peanut allergy. J Allergy Clin Immunol 1989;83:900-4
- Gupta RS, Springston EE, Warrier MR, et al. The prevalence, severity, and distribution of childhood food allergy in the United States. Pediatrics 2011;128:e9-17
- Liew WK, Williamson E, Tang ML. Anaphylaxis fatalities and admissions in Australia. J Allergy Clin Immunol 2009;123:434-42
- Bock SA, Munoz-Furlong A, Sampson HA. Further fatalities caused by anaphylactic reactions to food, 2001-2006. J Allergy Clin Immunol 2007;119:1016-8
- Pumphrey RS, Gowland MH. Further fatal allergic reactions to food in the United Kingdom, 1999-2006. J Allergy Clin Immunol 2007;119:1018-9
- Avery NJ, King RM, Knight S, et al. Assessment of quality of life in children with peanut allergy. Pediatr Allergy Immunol. 2003 Oct;14(5):378-82