There is a lot of confusion about food sensitivities and why people are reacting so much to the food they are eating. Many people experience adverse reactions to food and believe they have food allergies when in fact they often have food intolerances. True food allergies always involve the immune system where as food intolerances are a whole other set of adverse reactions that people experience to food. This article explains the main differences to help you understand the different types of adverse food reactions.
What are food allergies?
A food allergy is a reaction to food that involves the immune system. An exaggerated immune reaction will occur in response to the introduction of a food into the body. The body believes the food is harmful and the immune system produces Immunoglobulins (antibodies) to attack it.
The immune system becomes hyper responsive which causes antibodies to attach to antigens. The antibodies mediate significant inflammatory processes as part of this defensive action and a variety of other internal reactions.These processes cause allergic symptoms which can range from mild to severe and potentially life threatening.
The most well known type of food reaction is an IgE mediated reaction which is known as a Type 1 Hypersensitivity Reaction.This is what is often classed as a “true food allergy”. There are other immune mediated food reactions, the most common other reaction is called a Delayed IgG-Mediated Hypersensitivity which is also known as a Type III Hypersensitivity Reaction.
Type 1 – Immediate Hypersensitivity Reactions
This type of allergic reaction is mediated through IgE antibodies. Typically IgE reactions occur less than 2 hours after eating the allergen.The IgE antibodies bind to mast cells (resident cells of connective tissues containing allergy mediators) and basophils (a type of white blood cell containing allergy mediators) located in human tissue.The next time the person comes into contact with the allergen the mast cells and basophils will release potent chemical mediators such as histamine causing an allergic reaction. Such a reaction may cause anaphylaxis which is a life-threatening reaction and requires immediate medical attention. This is often called a true allergy, people who have this type of allergy usually know they have them as the symptoms are very noticeable and they often appear at an early age.
If you have an IgE reaction to food then the allergic food will need to be strictly avoided as reactions can be life-threatening.
Typical type 1 hypersensitivity responses are: runny nose, itchy eyes, wheezing, diarrhoea, swelling, restricted airways, rash, hives.
Type III – Delayed Hypersensitivity Reactions.
This type of reaction can involve IgG and IgE antibodies but more commonly involves IgG antibodies. IgG forms an immune complex with the allergen/antigen(Ag), which activate the complement pathway and releases inflammatory mediators wherever the immune complex is deposited. This can take anywhere from several hours to several days which is why the hypersensitivity reactions are delayed. Although macrophages (white blood cells) pick up the IgG-Ag complexes immediately, they have a finite capacity to do so. If there are a lot of antigens present, the macrophages may saturate their capacity to remove the immune complexes, causing the excess complexes to be deposited in tissue.
The type III symptoms can be broad and varied such as rashes, urticaria, asthma, stiffness, pain and swelling in joints, eczema or psoriasis, migraines and IBS type symptoms.
What is a food intolerance?
A food intolerance is characterized by an inability to digest food due to a non-immunological cause such as an enzyme deficiency or metabolic disorder. Some examples are:
A common example is lactose intolerance where a deficiency in the enzyme lactase can result in the reduced ability to break down lactose into the more simple sugars glucose and galactose in the small intestine. This can result in increased flatulence, bloating, diarrhea and other digestive complaints. The threshold for tolerance when it comes to symptoms appearing may depend upon dose of lactose consumed, gut transit time, small intestinal bacterial overgrowth and gut microbiome composition.
Not all food reactions to dairy are due to lactose intolerance, so consuming lactose free dairy products is not going to help in these situations. For example some people react to casein or whey, the protein components in milk. This can often (but not always) result in a more delayed reaction after consumption of dairy.
Other well known known food intolerances are when an individual experiences a reaction to FODMAPs (a collection of short chain carbohydrates and sugar alcohols found in foods, this is classed as an enzymatic deficiency where there is a lack of enzymes to these carbohydrates.
Gluten Intolerance or Non Celiac Gluten Sensitivity
Gluten Intolerance also known as Non-Celiac-Gluten-Sensitivity is also known as gluten intolerance. Although becoming increasingly recognised in medical literature, research is still attempting to determine if people who suffer from this are truly sensitive to wheat or in fact sensitive to other non-gluten components of wheat. Many natural healthcare practitioners (and I am one of them who has seen improvement again and again in clients after the removal of gluten) often recommend gluten free diets as clinical experience demonstrates improvement in many people's symptoms. Symptoms can range from digestive disorders to headaches, migraines, foggy thinking, eczema type rashes and fatigue.
There are also other adverse food reactions which are often classed as food intolerances:
Histamine, Amines & Salicylates
These are reactions that occur in response to pharmacological food constituents such as amines, salicylates and histamine. With histamine intolerance for example there is poor intestinal breakdown of histamine after ingesting histamine rich foods such as fermented foods, berries and aged cheeses, this can cause excessive histamine accumulation and a profound inflammatory response which can cause a variety of symptoms.
The above are some of the most common adverse reactions to food but by no means them all! There are many other adverse food sensitivities that people experience such as:
- Caffeine sensitivity which can cause shaking, headaches, migraines and changes in mood.
- Sensitivity to nightshade vegetables which are known to cause rashes, inflammation, pain and make arthritis symptoms worse. The reaction can be to the solanine or salicylate component of nightshade vegetables. Symptoms can vary depending on what component the individual is reacting to.
- Sensitivity to food additives and flavour enhancers such as MSG which can affect mood, behaviour, cause headaches, contribute to respiratory issues, skin rashes and other skin reactions.
- Sensitivity to garlic, onions, leeks and other members of the allium family. This is often due to the sulphur component of these foods, this can cause flatulence, bloating, nausea, IBS type symptoms.
- Legume intolerance which can cause bloating, flatulence, digestive discomfort and pain. These symptoms can greatly be reduced by proper preparation and soaking of beans and legumes.
- Sensitivity to nitrates which are preservatives in cured and canned food, they may contribute to headaches, behaviour changes and skin rashes.