Allergy vs. intolerance what's the difference?
They're often used to mean the same thing, but they're not. Here's how to tell them apart, and what to do next
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Three words, three different things
Allergy, intolerance and sensitivity get mixed up all the time. Knowing which is which matters, because it changes what you should do next.
Allergy
Involves: the immune system
Your immune system overreacts to a protein in a food. Reactions are usually quick, can be triggered by tiny amounts and can be serious.
Intolerance
Involves: the digestive system
Your body finds a food harder to digest or process, often because it's short of a particular enzyme. Symptoms are uncomfortable but not dangerous.
Sensitivity
Involves: no single body system
A broader word for foods or items you feel you don't get along with. It isn't a medical diagnosis, and there's no single agreed test for it.
Allergy or intolerance?
Food allergy
What's happening
Your immune system mistakes a protein in a food for a threat and releases chemicals such as histamine to fight it.
How quickly, how much
Usually within minutes, and typically within two hours. Even a trace amount can trigger a reaction, so the food needs to be avoided completely.
Common signs
Hives, itching, swelling of the lips, tongue or throat, vomiting, wheezing or trouble breathing. A severe reaction (anaphylaxis) is a medical emergency, so call 999.
How it's diagnosed
By a doctor or allergist, using skin prick tests, blood tests or a supervised food challenge.
Food intolerance
What's happening
Your digestive system has trouble breaking down or processing a food. Lactose intolerance, for example, happens when your body doesn't make enough of the enzyme lactase.
How quickly, how much
Often a few hours later, sometimes not until the next day. It usually depends on how much you eat, and many people can manage small amounts.
Common signs
Bloating, gas, stomach pain, nausea or diarrhoea. These are unpleasant, but not life-threatening.
How it's diagnosed
Usually with a food and symptom diary and an elimination diet, sometimes alongside tests such as a hydrogen breath test for lactose.
Where does sensitivity fit?
"Sensitivity" is the word you'll see most often, and the least clearly defined. People use it for foods or everyday items they feel they don't get along with, when there's no allergy and no obvious intolerance. There's no single medical definition and no standard test.
That's where our test comes in. Simply Sensitivity Checks uses bioresonance, a complementary wellness approach, to compare a few strands of your hair against hundreds of everyday items. You get a personalised report to help you decide which foods and items to look at more closely.
To be clear, bioresonance isn't recognised by mainstream medicine or backed by good-quality clinical research, and our test isn't an allergy test. It can't diagnose allergies or intolerances.
Is our test right for you?
Our test is a wellness tool, not a medical one. Here's a quick way to check whether it's the right next step.
It may suit you if
- You've already ruled out a food allergy with your doctor
- You'd like a starting point for a food diary or elimination diet
- You're curious about everyday foods and items you may want to explore
- You want a simple, needle-free test you can do at home
See a doctor first if
- You've had hives, swelling or trouble breathing after eating
- You think you or your child may have a food allergy
- You have symptoms such as weight loss, blood in your stool or diarrhoea that won't go away
- You're pregnant or breastfeeding, or the test is for a child under 6
Think a food doesn't agree with you?
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Rule out an allergy
If there's any chance it's an allergy, see your doctor or an allergist before changing anything.
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Keep a diary
Note what you eat and drink, and how you feel, for two to four weeks to spot any patterns.
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Remove and observe
Cut out one or a few suspect foods for a few weeks, ideally with help from a registered dietitian. Your report can help you decide where to start.
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Reintroduce slowly
Bring foods back one at a time and note any changes. Never reintroduce a food you know you're allergic to.
Allergy and intolerance FAQs
Can you develop a food allergy as an adult?
Yes. Food allergies can start at any age, including to foods you've eaten for years without a problem. Some childhood allergies, such as milk and egg, are often outgrown, while others, such as peanut and tree nut, usually last for life. If you notice new symptoms after eating, talk to your doctor.
Is lactose intolerance the same as a milk allergy?
No. Lactose intolerance is a digestive issue: your body doesn't make enough lactase to break down the natural sugar in milk. A milk allergy is an immune reaction to the proteins in milk, and it can be serious. Lactose-free milk is usually fine for lactose intolerance, but it isn't safe for someone with a milk allergy.
Is gluten intolerance the same as coeliac disease?
No. Coeliac disease is an autoimmune condition, where eating gluten damages the lining of the small intestine. It's diagnosed by a doctor, usually with a blood test followed by a biopsy. Non-coeliac gluten sensitivity is diagnosed by ruling out coeliac disease and wheat allergy first.
If you think gluten is a problem, ask your doctor about coeliac testing before you cut it out, because removing gluten first can affect the results.
What are the most common food allergens in the UK?
Nine foods cause most allergic reactions in the UK and must be clearly labelled on packaged foods: milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans and sesame.
Is a sensitivity the same as an intolerance?
The two words are often used to mean the same thing. "Intolerance" usually describes a specific digestive problem, such as lactose intolerance, while "sensitivity" is a broader, everyday term with no single medical definition.
Can your test detect allergies?
No. Our hair test isn't an allergy test and can't detect or diagnose allergies or intolerances. It doesn't test for medically recognised allergies, so a green or low result doesn't mean an item is safe for someone with a known allergy.
Can I take your test if I have a diagnosed allergy?
Yes, but keep avoiding that food exactly as your doctor has advised, whatever your report says. Your results aren't a substitute for medical advice and should never be used to decide whether to reintroduce a food you're allergic to.