Food allergy or food intolerance – what’s the difference?
Understanding the difference between a food allergy and a food intolerance can be confusing. Some of the symptoms experienced are similar, so it easy to see why you might be unclear.
Let’s try make this a bit clearer and give you some useful information.
The difference between a food allergy and an intolerance (or sensitivity) is how your body responds. If you have a food allergy, it is your immune system that causes the reaction which can be severe whereas if you have a food intolerance, the reaction is triggered by your digestive system.
Food Allergies
Food allergy is caused by your body’s immune system reacting to an allergen (protein) in food that it wrongly recognises as a toxic substance. Symptoms include:
- Tingling or itching in the mouth
- Hives, itching or eczema
- Swelling of the lips, face, tongue and throat or other parts of the body
- Wheezing, nasal congestion or trouble breathing
- Abdominal pain, diarrohea, nausea or vomiting
- Dizziness, lightheadedness or fainting
Depending on the symptoms and when they occur, food allergy can be divided into three types.
- IgE-mediated food allergy
This is the most common type which is triggered by the immune system producing an antibody called immunoglobulin (IgE). Symptoms occur quickly within a few seconds or minutes of eating.
- Non-IgE-mediated food allergy
These allergic reactions aren’t caused by IgE, but by other cells in the immune system. This type of allergy is often difficult to diagnose as symptoms can take up to several hours to develop.
- Mixed IgE and non-IgE-mediated food allergies
Some people may experience symptoms from both types.
Symptoms can be very severe and sometimes fatal if not treated quickly for example with an epipen which patients with a food allergy are often prescribed.
The overall prevalence of food allergy worldwide has increased over the last 30 years. The increase is multi-faceted with no single explanation. Increased frequencies have been associated with western lifestyles with urban areas showing more prevalence than rural. Our diets are changing with global access to foods not previously available or foods being used more often. There is also evidence that being more hygienic is linked to increasing allergy as we are not exposed to as many childhood infections. Awareness has also increased with publicity on high-profile food allergy in particular in the popular press.
There are eight foods which account for 90% of allergic reactions: milk, fish, peanuts, tree nuts, eggs, shellfish, wheat and soybeans. However, there are many other foods that people have been seen to be allergic to.
Food Intolerance
Food intolerances and sensitivities are more common than food allergies. Unlike an allergy, they are triggered by an intolerance in your digestive tract and are not immune-mediated. This is where your body cannot process or digest a food.
You may be sensitive or intolerant to a food for a variety of reasons including:
- Not having the right enzymes you need to digest a certain food
- Reactions to food additives or preservatives like sulphites, monosodium glutamate or artificial colours
- Pharmacological factors like a sensitivity to caffeine or other chemicals
- Sensitivity to the sugars found naturally found in certain foods like onions, broccoli or brussels sprouts.
Symptoms of food intolerance can vary but all are digestive-related including gas, bloating, diarrhoea, constipation, cramping and nausea.
Examples of intolerances include:
- Lactose where your body is unable to breakdown or digest lactose. Lactose is a sugar found in milk and milk products. It occurs when your small intestine doesn’t make enough of a digestive enzyme called lactase which breaks down lactose so your body can absorb it.
- Fructose malabsorption is where your body cannot absorb fructose. Fructose is a natural sugar that’s found in fruit, some vegetables, and honey.
- Gluten sensitivity can occur in the absence of coeliac disease in which immune reaction to gluten causes damage to the lining of the gut and hence produces symptoms of malabsorption. Non-coeliac gluten sensitivity is a recognised condition where symptoms may occur to gluten ingestion in the absence of coeliac disease.
