There's a lot of confusion over the difference between food intolerance and food allergy and this article will summarise the difference.

Food Intolerance

Food intolerance is a delayed reaction which occurs when the body is unable to completely break food down into absorbable components, due to an insufficient amount of digestive enzymes e.g. lactose intolerance, to a pharmacological effect (chemical sensitivity) e.g. tyramine in red wine, or IgG (immunoglobulin G) antibody reaction to the food.

In enzyme insufficiency, the food remains undigested in the small intestine, it exerts an osmotic effect, which means that salts and fluids are drawn in to the small intestine. This mixture moves rapidly into the large intestine, where it provides an ideal environment for the bacteria that normally reside there without doing any harm, to ferment the undigested foods.

When the foods are fermented, different substances and gases are produced, including carbon dioxide, methane, hydrogen and hydrogen sulphide - all causing bloating, cramping, wind and general discomfort. Other substances produced are re-absorbed into the body where they can produce feelings of nausea and headaches etc...

If undigested food remnants pass through the small intestine wall into the bloodstream, rather than passing into the large intestine mixed with salts and fluids, the immune system recognises these as 'foreign' and and launches an attack by using IgG (immunoglobulin G) antibodies to destroy them. In some people, especially after food poisoning or other gastro-intestinal illness or disease, the small intestine wall becomes inflamed or irritated. This allows partially digested foods to leak into the bloodstream, which causes the IgG reaction; in this case, the condition is known as 'leaky gut syndrome', and people with this typically have multiple food intolerances.

Food intolerances are not generally life-threatening, but can be very unpleasant.

If after eating you regularly experience the following symptoms, then you may have a food intolerance:

• Bloating / stomach pain
• Diarrhoea / constipation
• Wind / "grumbly tummy"
• Headache / migraine
• Lack of energy / constant tiredness / lethargy
• Food cravings especially for wheat (bread, pasta) or dairy foods

Food Allergy

Allergies are caused when a substance, called an allergen, comes into contact with the body. The immune system thinks the allergen is an 'invader' and launches an attack by using IgE (immunoglobulin E) antibodies. These IgE antibodies release histamine to destroy the allergen but this also causes the allergic reaction.

If after eating you regularly experience the following symptoms, then you may have a food allergy:

• Tingling on or around the lips and tongue
• Itching around the mouth area
• Swelling in the mouth or throat
• Streaming eyes or nose
• Acute nausea or vomiting
• Wheezing or breathing difficulties
• Rash anywhere on the body