What Is A Food Allergy?
Food allergies (FA) are when the body reacts in an exaggerated and negative way to certain foods. These reactions are mediated by the immune system, whose role is to defend the body against harmful or infectious organisms including viruses and bacteria, and other harmful substances or foreign bodies. In allergic reactions to foods, the immune system elicits an inappropriate response to naturally-occurring proteins, in which these proteins are perceived as a ‘threat’ or an antigen – something that could potentially be harmful . Allergic reactions to foods vary widely in terms of severity, from very mild to potentially fatal. They can include, in any order or combination (read more about each symptom by clicking the link):
- Skin redness or rashes (urticaria) and itching (pruritis), eczema
- Wheezing, breathing difficulties or nasal congestion
- Swelling of the tongue, lips, face or other parts of the body
- Dizziness, lightheadedness or fainting
- Abdominal pain, diahorrea
- Nausea and vomiting
- Tingling or itching in the mouth; odd taste in the mouth
*Please note: These are the most common symptoms – this list is not exhaustive*
What Is A Food Intolerance?
There are many similarities between food intolerances and FA. Indeed, some conditions can be classified as both based on the severity of the reaction, such as Food Protein-Induced Enterocolitis Syndrome (FPIES) and coeliac disease. FPIES is a severe gastrointestinal reaction that generally occurs two to six hours after the consumption of milk, soya, certain grains, and some other solid foods. It mainly affects babies. Coeliac disease is caused by a severe intolerance of gluten, a protein that occurs naturally in many grains such as wheat.
A food intolerance may cause a similar reaction to an FA, such as abdominal cramping, nausea or vomiting. The main difference is that it may be possible to ingest small amounts of the trigger foods without any ill effect; whereas in the case of a true allergy, ingestion of even the smallest amount of allergenic foods will trigger a reaction. Other examples of food intolerances include: pollen-food allergy syndrome, allergenic proctocolitis and eosinophilic oesophagitis. These will be discussed in more detail in further articles.
Sampath V, Tupa D, Graham MT, Chatila TA, Spergel JM, Nadeau KC (2017). ‘Deciphering the black box of food allergy mechanisms’. Ann Allergy Asthma Immunol. 118(1): 21-27. doi: 10.1016/j.anai.2016.10.017