How to tell the difference:
The signs of a food allergy are:
- It produces acute distinctive symptoms, usually within seconds or minutes.
- In extreme cases, it can be life-threatening.
- It doesn't depend on the amount of food eaten. A tiny trace of the problem food can cause a reaction.
- The problem food is never craved.
- An expert can diagnose the food through several tests, and taking your medical history.
The signs of food intolerance are:
- It produces delayed, long-lasting symptoms, which mainly involve the digestive system.
- It's never life-threatening.
- It usually depends on the amount eaten. A reasonable portion of food is needed to cause a reaction.
- The problem food may be craved.
- It's difficult to diagnose. Only a few reliable tests are available.
Genuine food allergy is rare. Less than 2% of the population (and 8% of children under the age of 3) are affected. Food intolerance is more common. Allergy UK estimates that up to 45% of people in the UK suffer from food intolerance (calculated as food-related symptoms), including migraines, skin rashes and problems with the gut.
The difference between a food allergy and food intolerance is not well understood. People who have symptoms that may be caused by food often don't know how to treat them.
What is a food allergy?
A food allergy is a rapid and serious response to a food by the immune system, the body’s defence system. If you have a food allergy, immune system antibodies (called IgE) mistake a food for an 'invader' and attack it. This causes an almost immediate reaction in which inflammatory substances are released into the body.
These cause sharp and unpleasant side effects, which are usually the classic allergy symptoms of rash, wheezing and itch. The most common food allergies among adults are peanuts and tree nuts, such as walnuts, hazelnuts and brazil nuts, fish and shellfish. Children often have allergies to milk and eggs as well to peanuts, tree nuts and fish.
What is a food intolerance?
Food intolerances are much more common than food allergies. The symptoms of food intolerance tend to occur more slowly, often many hours after eating the problem food. It’s possible to be intolerant to several different foods. This can make it difficult to identify which foods are causing the problem. Lactose intolerance and coeliac disease are types of food intolerance.
Could it be lactose intolerance?
This occurs when your body can't digest milk, sugar or lactose. Lactose is found in all dairy foods. The main symptoms are diarrhoea and stomach pain. In most cases, your GP can diagnose lactose intolerance by looking at your symptoms and medical history.
Could it be coeliac disease?
Coeliac disease is a gut disorder caused by gluten (a protein found in wheat, rye, barley and oats), which damages the intestine. Symptoms include diarrhoea, wind, weight loss and mouth ulcers. About one in 100 people in the UK have coeliac disease. Around half a million aren't diagnosed. Reliable tests are available.
Could it be another type of food intolerance?
Sometimes it isn't clear why a food may be causing a problem. The only reliable way of identifying such an intolerance is through an exclusion diet.
Could it be psychological?
Psychological food intolerance is called food aversion. For some people, thinking about a food or believing they react to it is enough to bring about a physical reaction. Dieticians specialising in food intolerance can help you to identify food aversion.
Could it be something else?
Your doctor may want to consider other possibilities, such as inflammatory bowel disease, gastrointestinal obstructions or irritable bowel syndrome (IBS).
What are the treatments?
In the case of a food allergy, you'll have to avoid the food, though you may be able to eat the cooked versions without any problems.
With lactose intolerance, you'll have to reduce the amount of dairy food that you eat.
With coeliac disease, you must avoid gluten for life. With other forms of food intolerance, you'll have to stop eating the food for a while, or possibly for life.
In all cases, always read food labels carefully, and learn where your problem food may be ‘hiding’ in other foods. A dietician can advise you on your diet.
