What's the Difference - Allergies vs Intolerance

Do you know the difference?

There's a lot of talk in the news about allergies and intolerances, and it can all get quite confusing. What's the difference between the two, and why does it matter?

Allergies and intolerances may seem similar, but they're actually quite different, and it's a good idea to know which is which.

The table below will help explain the main differences between food allergies and intolerances. (Important note: this information is intended as advice only; if you think your child may have a food allergy or intolerance, you should always contact your health visitor or GP for more information.)

Food AllergyFood Intolerance
What is it?An adverse immune response to a specific protein within a food.An adverse bodily response to a component within a food (not necessarily a protein) with no immune involvement.
Common or rare?Rare, but risk is higher in families with a history of allergy.More common than an allergy, but still unusual in children.
What causes it?The immune system thinks the protein in the food is harmful and reacts to it, causing symptoms (see below).There are a number of causes; sometimes a lack of enzymes means food can’t get digested, or sometimes foods can cause symptoms on their own.
AmountsA reaction can be caused by the smallest traces of the food.Usually a reaction only happens after consuming at least a teaspoon of the food.
SymptomsRedness, swelling, difficulty breathing, skin reactions including itching or urticaria (hives) and anaphylaxis, among others.Headache, bloating, stomachache, diarrhoea, sickness. No anaphylaxis.
How is it diagnosed?Generally: look at previous medical conditions and rule out other causes. Then either a skin prick test (SPT) or blood test (called a RAST) or skin patch test (performed by GP or allergist).Could involve looking at previous medical conditions and ruling out other causes. Then either keeping a food and symptom diary, or trying an ‘exclusion diet’ where foods are avoided and then re-introduced to see if they cause symptoms.
Is there a cure?Avoiding the food completely is the only treatment – however, some children do ‘grow out’ of their allergies.If the intolerance is severe the food may need to be avoided for life, or limited to small amounts.
How is it managed?For some, mild symptoms can be controlled with anti-histamines. You may need to keep adrenaline (an EpiPen) on hand if the allergy is severe. If the food is a major part of the diet, nutritional advice may be needed. Re-challenges may be performed under medical supervision to see if the allergy persists into adulthood.If the food is a major part of the diet, nutritional advice may be needed.Adrenaline is not required. As some children can ‘grow out of’ food intolerances, re-challenges may be performed under medical supervision.

Allergy and intolerance FAQ

What is anaphylaxis?

Anaphylaxis is a type of allergic reaction which affects the whole body and can be life-threatening. Thankfully, it is very rare; however, if it occurs it requires immediate medical treatment, which is why all allergies should be taken seriously.

Anaphylaxis usually occurs within a few minutes of exposure to the allergen, but can take a few hours to develop. The symptoms vary, but might include skin redness, urticaria (hives) appearing on the body, itching or swelling in the mouth and throat, difficulty in swallowing or speaking, a rapid heartbeat, wheezing or worsening of asthma, feeling sick or vomiting, a drop in blood pressure (the person may feel weak or fall down) and unconsciousness.

If you believe that your child may be experiencing anaphylaxis, then you need to immediately seek medical advice by calling 999 and following their instructions. Usually anaphylaxis is treated with injectable adrenaline (an EpiPen), and some people who have had anaphylaxis in the past carry this with them just in case.

What should I do if I think my child has an allergy/intolerance?

If you suspect that your child may have an abnormal reaction to a food, it's important to discuss it with your GP. Sometimes what looks like an allergy or an intolerance might be something different, so you don’t want to take things out of your child’s diet until you're certain of the cause.

If the symptoms were obviously related to one specific food (for example, an egg) then it may be wise to avoid giving your child egg until you have a chance to speak to the GP. Even if you do this and the symptoms stop, you should still book an appointment to see your GP so you can have your concerns confirmed and properly diagnosed.

It may help you to write down what your child ate and exactly what happened so that you don’t forget anything which may be important when you see your doctor; this will also help them to make the right diagnosis.

What sorts of foods are likely to trigger an allergy?

Any food containing protein has the potential to trigger an allergy; however, there some are more common culprits than others, including peanuts, tree nuts, fish and shellfish, cow’s milk, eggs, soya and wheat.

What sorts of foods are likely to cause intolerance?

We don't really know what makes a food likely to cause intolerance; however, lactose, a milk sugar, is the most common offender. Lactose-intolerant people produce less of the enzyme the body needs to break down lactose, which can lead to uncomfortable symptoms.