Allergy & Intolerance
It has been known for thousands of years that some susceptible people have unpleasant reactions to certain types of foods. These days we now know a lot more about the problem, the reasons for it, and why only some people suffer from such reactions.
Someone who suffers from an abnormal, unpleasant reaction to a particular food is said to be ‘sensitive’ to that food. It can give rise to a wide range of symptoms. It can simply be a feeling of being bloated, abdominal pains or headaches, to severe adverse reactions like those caused by nuts in certain individuals.
Perhaps the most well-known reaction to food is sensitivity to nuts. Some people have a severe reaction to even the slightest trace of nuts in their food. Labels now reveal if foods contain nuts or nut products. Great care is taken over food hygiene to prevent accidental contamination of foods with even the smallest trace of nuts.
Research suggests that around 1 person in every 50 has some form of food sensitivity. Less than 0.25% of people suffer from reactions to food additives. That is just 1 person in every 400. In other words you are more likely to suffer a bad reaction to a natural foodstuff than to an additive.
What is an allergic reaction?
An allergic reaction happens when the immune system reacts to a substance from outside the body. This could be pollen (hay fever), pet hairs (asthma) or molecules in foods such as nuts and milk. The immune system of a healthy individual is unaffected by these normally harmless molecules, but the immune system of the allergic individual reacts as if the body is under attack. It releases powerful chemicals called histamine that cause the unpleasant symptoms of an allergic reaction. Allergy is essentially ‘immunity gone wrong.’
About 90% of all cases of food allergy involve wheat, eggs, peanuts (groundnuts), tree nuts (including walnuts, brazil nuts, hazelnuts and almonds), milk, shellfish, fish and soy.
Very few people are allergic to food additives.
Anaphylaxis is the most serious form of allergic reaction. The throat and windpipe can swell so that the person cannot breathe. This can cause death if not treated quickly. Someone who knows they are at risk of suffering from anaphylaxis may carry a pen-syringe containing adrenalin. This antidote can relieve the symptoms if given quickly enough.
People who are sensitive to a particular food often assume they are ‘allergic’ to that food. This is often the case, but an allergic reaction is triggered by the body’s immune system and there are other adverse reactions to food that do not involve the immune system. The term ‘food intolerance’ is used to describe this type of abnormal reaction. The symptoms experienced (rashes, headaches or feeling bloated) are similar to allergic reactions, but the mechanism is different.
Table showing the types of problems that can be caused by an allergic reaction
| Intolerance | Comments |
|---|---|
| Lactose intolerance (alactasia) | Common form of intolerance to cow’s milk found in people who lack the enzyme lactase and consumption of dairy products makes them sick. This means they cannot digest the milk sugar |
| Naturally occurring (biogenic) amines | The amines histamine and tyramine can reach high levels in cheese, some wines, tuna and mackerel. If these foods are eaten, they can cause adverse reactions in susceptible individuals |
| Food additives | Certain colours, preservatives and anti-oxidants, can also cause adverse reactions in susceptible individuals. If a person has bad reaction to a food additive it is thought that this is because they already have some form of a problem and this is made worse by the additive rather than caused by it |
| Sulfites | In high concentrations, these can affect a small sub-group of people with severe asthma. Steroid-dependent asthmatics are most at risk and anaphylactic type reactions, eg. severe breathing problems, are reported to have occurred on occasions |
| Benzoates | Can affect asthmatics and aggravate dermatitis (inflamed skin) |
| Azo dyes | These have been linked to a variety of symptoms, eg. skin rash, asthma and dermatitis. It is well established that tartrazine and other azo dyes can occasionally provoke skin rash. Tartrazine is also known to have affected patients with dermatitis |
| Chinese Restaurant Syndrome | Chinese foods can contain a lot of the flavour enhancer monosodium glutamate (MSG). It has been linked with people who suffer reactions after eating Chinese meals. However, tests have not shown a link with MSG and the problems are most likely caused by other compounds such as naturally occurring histamine in the ingredients |