The difference between a food allergy (IgE) & a food intolerance (IgG)

Everything we eat can elicit a positive or negative reaction in the body. If you are intolerant to a certain food and you continue to eat it, your body will mount an inflammatory reaction that may manifest in a variety of conditions that affect your lifestyle such as severe headaches, chronic pain, digestive disorders and other issues. Food intolerance can be caused by several factors including irritable bowel syndrome (IBS), food poisoning, psychological factors and sensitivity to certain processed or natural food additives. Studies show that less than 2% of the population suffers from food allergies, however up to 45% of the population is estimated to suffer from some form of food intolerance. In the case of children with autism, food intolerances have been shown to affect mood, behavior and anxiety levels and once identified and removed from the diet, these children experience a healthier, calmer existence.   

Following are some key differences between food allergies and food intolerance:

Food Allergies

·       Usually come on suddenly

·       A small amount of food can trigger a reaction

·       Happen every time the food is eaten

·       Can be life-threatening

·       Are usually identified during childhood

Food Intolerance

·       Occurs when a food irritates your stomach or your body can’t properly digest it

·       Symptoms include: gas, cramps, bloating, heartburn, anxiety, migraines, joint pains, skin problems, fatigue, depression, irritability and an inability to lose weight on a diet.

·       Symptoms may appear immediately or days after eating the type of food you’re intolerant to

·       Usually develops gradually, with symptoms sometimes not appearing before turning 30 years-old

·       May happen when you eat a lot of the food

·       May happen if you eat the food often

·       Is not life-threatening

Most food allergy tests that are performed look at the reaction of the body’s IgE immune cells to various food types. An IgE reaction is a true allergy.  This is something an allergist can test through:

·       a blood test to a food, pollen, dust, animal hair, etc.  T

·       hey can also look for an IgE reaction through skin prick testing.

How does an IgE reaction look like?

An IgE reaction is usually quite obvious.  It can often happen within minutes of eating something.  We’ve all heard of cases where someone reacts to peanuts or strawberries or pineapples or shell fish.  In some types of reactions that are immediate after ingesting a food, hives may develop on the body, lips may swell, eyes may get runny or the throat may become very itchy.  In severe cases an allergic reaction can lead to anaphylactic reaction or anaphylactic shock. Someone who has a true allergy to bee stings for example can develop and anaphylactic reaction resulting in difficulty breathing and will need to be hospitalized to take medication to short circuit that reaction. It is important to know if and what your child is allergic to, but usually these can only be identified by skin tests or a blood test during or very close to the time a reaction is actually happening and there is enough IgE circulating in the blood stream to be picked up by the test.  

Most reactions to foods we come in to contact with and are testing for are actually not IgE reactions but IgGreactions.  IgG is the most abundant immune chemical (antibody) in the body that can sometimes react with food quite adversely leading to low level inflammatory and immune reactions in the body.  These reactions are called IgG delayed hypersensitivity reactions. They are not life threatening and often not immediate – making them different in that sense to allergic reactions - but in the digestive system they can quickly cause bloating, gas, diarrhea. In the long run, these food ‘intolerances’ can lead to low level inflammation that in turn can lead to joint pain, muscle pain, fatigue, migraines, weight gain, insomnia, anxiety and depression and several other symptoms.

Thus, a food IgG reaction, even though sometimes it is called an allergic reaction, is truly not an allergy but rather a hypersensitivity or an intolerance to food proteins. When you perform a food intolerance test, depending on the lab and the test type, you can test your IgG response to a panel of over 200 different foods types or more that you or your child are eating.