Difference between Food Allergy and Food Intolerance

There is much misunderstanding about these terms and they are frequently confused. Many people speak of food allergy when what they describe is likely to be food intolerance.

(Use the Glossary to find out word meanings and pronunciations.)

To clarify:

Food allergy is a rather fast response (minutes) by the body’s immune system to a perceived invader. Signs or symptoms are typically immediate, dramatic and visible: coughing, sneezing, vomiting, migraines, watering eyes, rashes, swelling tissue, hives – or in severe cases an anaphylactic shock which requires emergency intervention. However other symptoms like the gastro-intestinal responses nausea, vomiting and diarrhea can be delayed for hours or even days.

Food intolerance on the other hand is rather slow onset reaction, hours, days or even weeks. It is an inability to process a particular food. It is also thought to be an immune system response. The gastro-intestinal tract in some people is simply unable to produce appropriate enzymes for normal chemical breakdown. The food passes through unprocessed, or lingers in the gut fermenting producing excess ‘gas’. In some cases protein fragments rupture the lining of the intestine allowing foreign particles into the bloodstream.

Symptoms of Food intolerance are much more delayed, less dramatic and lifestyle threatening rather than life threatening. They generally manifest as nutritional deficiencies that develop over time. If left untreated however they can lead to serious illness and tissue damage. Health Risks

Many people wonder why they discover they have food intolerance as adults. Why, they ask, was I able to digest these foods for all those years? The answer is that there was always a reaction to this food going on in your body and an associated stress.

But as you continue to consume it two or three times a day the body adapts, in its wonderful natural way. Your reactions manifest less, masking the symptoms.

However a bout of illness or a stressful period or a course of anti-biotics can render your body less able to cope. As the immune system weakens, malabsorption symptoms like iron deficiency may begin to show. These are often the most telling indicators of a long-term food intolerance.

Another long-term consequence is that you begin to crave those very foods:

• I could live without anything else she says, but I could never give up bread! (or wine or chocolate or cheese). See Food addiction below.

More about food intolerance

More about food allergy

An Allergy triggers an allergic response in a person – often immediately - on exposure to the allergen. Generally, people suffering from an allergy have had a breakdown in their immune system: it “misreads” the allergen as an enemy invader and pulls out all stops to attack it.

What it means is that while an allergic person reacts quite dramatically to the first exposure (coughing, sneezing etc), the reactions to second and subsequent exposures can be greatly amplified, due to the immune system being primed and ready to spring into full defensive action. This is when the anaphylactic response can occur (see below).

Normally our immune system protects us by producing antibodies in the blood that attack bacteria and viruses invading our bodies. This lets us fight off infections without ever knowing they were there. But in a very few people the immune system produces an abnormal type of antibody in response to things like pollens, or in some cases certain foods.

Many food allergy symptoms are the same as regular allergy symptoms (those in response to pollens, chemicals and animal hair): sneezing, skin rashes, hives, watering eyes, runny nose and sore throat. For food allergies add nausea, spontaneous vomiting and gastro-intestinal symptoms like diarrhea.

For a fuller description refer to the Symptoms Matrix and the Understanding Food Allergies page.

Anaphylactic Shock

In severe cases there is an anaphylactic response where the sufferer’s tissues become hypersensitive and swell up to two or three times their normal size. A swollen nose is a classic allergic symptom. Histamines have caused the internal tissue cells to retain excess fluids. While a stuffy nose is a nuisance it is not serious.

An anaphylactic response however is when this happens in the tissues of the tongue, mouth and throat. These hypersensitive tissues swell up so rapidly that they obstruct breathing. These allergy sufferers gasp for air and can suffocate and die if not given emergency treatment (eg. by the administration of adrenalin by paramedics, teachers, carers or medical staff.

Fortunately food allergy is rather rare. Less than 1% of people suffer true food allergies. However, because Food allergy is more visible than food intolerance – it is better diagnosed.

The discovery of a food allergy is usually a dramatic event, particularly in children, calling for a regime of strict dietary supervision. Luckily the more stringent food labelling laws recently introduced in Australia go some way towards assisting with food allergies.

You might have seen on a food label that it “may contain traces of nuts”. Nuts - especially peanuts - contain some of the world’s worst offending allergens.

Other foods known to cause allergic reactions are eggs, strawberries, milk protein, wheat, soy and seafood: crustaceans like crab, lobster and prawns; or shellfish – like scallops, oysters and clams. Foods containing additives and colourings are also widely recognised as causes of allergic responses.

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More about food intolerance

Food intolerance is an inability to properly digest certain foods. In some cases food passes right through the body before digestion is complete – so is eliminated only partially processed like milk products causing diarrhea. In other cases some foods have components which actually attack the lining of the gut and damage it every time that food is eaten (like Celiacs with gluten). Fortunately most food intolerant people recover fully when the offending food is avoided.

Direct problems such as severe abdominal cramps, bloating, flatulence, diarrhea and hemorrhoids are common. However the indirect problems associated with poor absorption can be much more harmful. When food leaves the body only partially processed many vital nutrients are lost too. People with food intolerance typically catch viruses easily, may have dry skin, hair and nail problems and tire easily.

Some become deficient in iron or calcium and suffer a further series of health issues like anaemia or osteoporosis.

Many food intolerant people are underweight due to their inability to get full nutrient value from foods. Of course with diarrhea there is the constant risk of dehydration especially among children and elderly people.

Others can be overweight often from an interference with the thyroid gland causing a disruption to normal metabolism.

Food addiction

It is thought that we can actually be addicted to the foods to which we are intolerant. The adrenalin rush (the classic “fight or flight” response) experienced after eating these foods is the ‘hook’ that keeps us coming back. But while sufferers feel good for a while, the ‘high’ soon passes and they go back to feeling drained and listless.

It may be prudent to examine these can’t-live-without foods as possible suspects.

Major symptoms of food intolerance (food sensitivity):

• gastro-intestinal (diarrhea, bloating etc.) and subsequent malabsorption problems like anaemia and osteoporosis
• respiratory system distress including bronchitis, breathlessness, sinusitis, congestion
• miscarriage; infertility in males and females
• a large number of skin irritations from eczema to dandruff
• a long list of general body ailments including headache, lethargy, migraine, inability to concentrate, sleep disorders, mouth ulcers, urinary problems, weight fluctuation and obsessive (addictive) eating
• see also serious disease from chronic untreated food intolerance

For a fuller description refer to the Symptoms Matrix.

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More information

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