There is a lot of confusion about the difference between a food allergy and a food intolerance, with the terms often being used interchangeably. However, there is actually a distinct and important difference between the two, with symptoms, severity and causes varying significantly.
A food allergy occurs when the immune system reacts to an otherwise harmless substance present in certain foods. Allergic reactions range from mild to severe. Reactions usually occur quickly and symptoms may include skin rashes such as eczema and hives, gastrointestinal issues such as nausea, vomiting, diarrhea, and abdominal pain or respiratory symptoms such as sneezing and asthma. Rarely, allergies can cause anaphylaxis, the most severe form of allergic reaction. The most common foods causing life-threatening anaphylaxis are peanuts, tree nuts, shellfish, milk and egg.
Food allergy is estimated to affect around 10% of children up to 1 year of age; between 4-8% of children aged up to 5 years of age and approximately 2% of adults.
Food intolerance is an adverse reaction to food in which the immune system is not involved. Intolerance to food can result from a deficiency of certain enzymes (e.g. lactase deficiency causes lactose intolerance), sensitivity to naturally occurring chemicals in foods such as histamine or from toxins present in food. Reactions are usually delayed, occurring several hours and sometimes up to several days after eating the offending food. Food intolerance does not cause severe allergic reactions such as anaphylaxis, with the symptoms usually delayed of a more chronic nature. They may include skin rashes, e.g. dermatitis or eczema, respiratory tract issues such as nasal congestion, sinusitis, and asthma or gastrointestinal symptoms such as abdominal cramping, nausea, diarrhea, constipation, and irritable bowel syndrome. Because the immune system is not involved, food intolerances do not show on food allergy testing such as skin prick tests.
Food Intolerance and FODMAPs
One of the most common causes of food intolerances are a group of carbohydrates (sugars) know as FODMAPs. FODMAPs are a collection of different sugars which are found naturally in many of the foods we eat. These sugars are usually absorbed in the small intestine, however, they are poorly absorbed by some people. They then stay in the gut and continue to the large intestine, where they act as a food source to the bacteria that live there normally. The bacteria then digest/ferment these sugars, resulting in the symptoms of irritable bowel syndrome (IBS) such as bloating, excess gas, abdominal pain, nausea and diarrhoea and constipation.
FODMAPs is an acronym for:
Oligosaccharides (eg. Fructans and Galacto-oligosaccharides (GOS))
Disaccharides (eg. Lactose)
Monosaccharides (eg. excess Fructose)
Polyols (eg. Sorbitol, Mannitol, Maltitol, Xylitol and Isomalt)
Some Common Sources of FODMAPs:
Excess fructose: honey, apples, mango, pear, watermelon, high fructose corn syrup
Fructans: garlic (in large amounts), leek, onion, spring onion, shallots, wheat, rye and barley (in large amounts)
Lactose: milk, ice cream, custard, yoghurt and soft unripened cheeses (eg. ricotta, cottage, cream, marscarpone).
Galacto-Oligosaccharides (GOS): Beans (eg. baked beans, kidney beans, bortolotti beans), lentils, chickpeas
Polyols: apples, apricots, avocado, cherries, nectarines, pears, plums, prunes, mushrooms, sugar alcohols such as sorbitol, mannitol and xylitol
Hydrogen Methane Testing for Food Intolerances
Hydrogen Methane Testing (HMT) is a simple and non-invasive breath test which is used to diagnose carbohydrate (sugar) intolerances. At The Breath Test Lab, we use Hydrogen & Methane Breath Tests to diagnose lactose, fructose, sorbitol, xylitol and sucrose malabsorption and intolerances. This method of diagnosis is a much simpler and easier alternative to a low FODMAP diet which requires restricting dietary intake of FODMAPs for an extended period and then gradually reintroducing them one at a time to determine which ones an individual is sensitive to.
For more information about Hydrogen Methane Testing, see our services page