Food Allergy Or Food Intolerance?
Two conditions that are very different.
It may come as something of a surprise, but food allergies may not be as common as you think. The term food allergy is often used to describe any adverse reaction that happens after eating a particular food.
But just one to three per cent of adults and up to eight per cent of children are estimated to have food allergies in the UK.
Food intolerances though, are much more common. Some surveys have suggested that between 20 to 30 per cent of people have suffered from a food intolerance, but this figure may be as high as 46 per cent, according to health charity Allergy UK.
During Food Allergy and Intolerance Week (23 - 29 January), here's a guide to how food allergies and food intolerances differ.
A true food allergy occurs when the body makes a specific immune response against a particular food protein. The culprit protein, or allergen, triggers an immune response which involves the production of IgE antibodies and the release of histamine from mast cells.
This reaction occurs within minutes to a few hours of coming into contact with just tiny amounts of the offending food, causing symptoms such as a red, itchy rash, shortness of breath or wheezing, runny eyes and nose, swelling lips and throat, abdominal pain, nausea, diarrhoea and vomiting.
In some cases, the allergen can trigger an extreme reaction, known as anaphylaxis, which can be life-threatening, nuts being a typical examples of this.
Although you can be allergic to any kind of food, around ninety per cent of food allergies are caused by allergens found in milk, eggs, peanuts, tree nuts (e.g. walnuts, hazelnuts and brazil nuts), fish, shellfish, soya and wheat.
Children often outgrow allergies to milk, eggs and soya, but allergies to peanuts, shellfish and fish are more likely to persist later in life.
Developing allergic symptoms within a short time of eating one food means that people quickly suspect they might have an allergy, but sometimes it's not so easy to pinpoint what's causing the allergic reaction.
A single allergen can cause a person to be allergic to a number of foods within a food group; for example, someone with a peanut allergy may also be allergic to other legumes such as beans or lentils.
And you can be allergic to more than one food allergen, which is why it's important to see your GP if you think you have a food allergy. They can refer you to an allergy clinic where they carry out skin and blood tests which can help to identify the allergens.
The clinic may conduct a double blind placebo controlled food challenge, regarded as the gold standard method for diagnosing allergies, where the person is given a number of foods, including the suspect one. Because of the risk of anaphylaxis, this must only be carried out in clinics with experienced staff.
Unlike a food allergy, the symptoms of a food intolerance - which can include nausea, bloating, abdominal pain and diarrhoea - are not linked to an immune reaction.
The symptoms of a food intolerance are usually more variable than those of a food allergy, are rarely life-threatening and take longer to develop after eating the food involved. However, it can still make your life miserable.
With a food allergy, coming into contact with trace amounts of the offending food can trigger a reaction, but with food intolerance, this may be dose-related, so a person can eat small amounts of a food without consequence, but greater amounts may cause problems.
Unlike a food allergy, food intolerances have multiple causes, which are often - but not always linked to the digestive system.
Milk, lactose, gluten, wheat, food additives and some naturally occurring compounds in foods are common causes of food intolerance.
Lactose intolerance, which affects around five per cent of people in the UK, is caused by the body not producing enough of the enzyme lactase, needed to break down the sugar lactose which is found in cow's milk. This prevents the sugar being absorbed into the bloodstream.
Caffeine, cheese, and chocolate are also known migraine triggers for some people.
Others are affected by food preservatives and additives such as the artificial colourant tartrazine, aspartame, sulphites, metabisulphites, benzoates, salicylates and monosodium glutamate.
Coeliac disease, often mistakenly referred to as gluten intolerance, is triggered by food containing gluten, which can trigger the immune system to attack the intestine. This condition can also have symptoms similar to those of a food intolerance. According to charity Coeliac UK, as many as half a million people in the UK may have the condition, but remain undiagnosed.
The range of symptoms, their similarity with other health conditions, their multiple causes and lack of proven and reliable diagnostic tests, makes most food intolerances difficult to diagnose.
The only way to identify the suspect food is through a process of elimination, where various foods are excluded from the person's diet, then individually introduced to pinpoint the cause of the symptoms.
This should not be undertaken without the help of your GP and/or registered dietician. It can be complicated as the culprit food substance may be present in other, unexpected foods.
Excluding entire food groups can lead to a nutrient deficiency which may leave you feeling worse than before.