Food Intolerance vs Food Allergy: How to Tell the Difference
By the GutBox team · · 6 min read
If certain foods seem to disagree with you, it's natural to wonder whether you're allergic to them. In most cases, what people experience is a food intolerance rather than an allergy. The two are often mixed up, but they're very different, and knowing which one you might be dealing with changes what you should do.
The key difference
| Food intolerance | Food allergy | |
|---|---|---|
| What happens | Your body has difficulty digesting a food or ingredient | Your immune system reacts to a food |
| Typical symptoms | Bloating, stomach pain, diarrhoea, wind, tiredness | Rashes, swelling, itching, breathing problems, stomach pain, being sick |
| Timing | Usually a few hours after eating | Often straight after eating, but can be later |
| Seriousness | Uncomfortable, but not usually serious | Often mild, but can be life-threatening |
Food intolerance
The NHS describes a food intolerance as when you have difficulty digesting certain foods or ingredients. It can be unpleasant, but it isn't usually serious.
Symptoms usually start a few hours after eating the food, and can last for hours or days. The most common are bloating, diarrhoea, stomach pain and tiredness. Some people also get headaches, joint pain or rashes.
Foods and ingredients the NHS lists as common causes include:
- Lactose, the sugar in milk and dairy products
- Gluten, found in wheat, barley and rye
- Caffeine and alcohol
- Histamine, found in some foods and drinks such as aged cheese and wine
- Additives such as sulphites, MSG and benzoates
Because symptoms are delayed, and can depend on how much you've eaten, intolerances are often hard to pin down from memory. That's why a food and symptom diary is so useful.
Food allergy
A food allergy is when your immune system reacts to a food. Symptoms can come on straight after eating, or sometimes later, and can include dizziness, an itchy rash, swelling of the face, sneezing or a blocked nose, breathing problems, feeling or being sick, stomach pain and diarrhoea.
The NHS lists cow's milk, eggs, peanuts, tree nuts, shellfish and wheat among the most common food allergies, although you can be allergic to any food.
How to work out what's affecting you
If you suspect an allergy
Speak to a GP. Allergies should be diagnosed properly, and you shouldn't test a suspected allergy yourself by eating the food again.
If you suspect an intolerance
The NHS recommends a careful, step-by-step approach:
- Keep a food and symptom diary. Record what you eat, your symptoms and when they happen.
- Look for patterns. Check whether a particular food keeps appearing in the hours before you feel unwell.
- Try leaving it out, then bring it back. Avoid the suspected food for a set time, then reintroduce it and see whether symptoms return.
The NHS also warns against cutting foods out without advice, because it can mean missing out on important nutrients. This is especially important for children. If you think you need to avoid a food long term, or several foods, speak to a GP, who may refer you to a dietitian.
What about home intolerance tests?
The NHS advises against commercial home intolerance tests. There's a lack of reliable evidence that they work, and they may lead you to cut out foods unnecessarily. For lactose intolerance, a GP may arrange tests such as a blood or breath test.
Tracking makes it easier
Spotting a delayed reaction is hard when you've eaten several meals since. GutBox puts your meals and symptoms on one timeline and highlights foods that keep showing up before symptoms. When one stands out, it suggests a short test to check, so you change one thing at a time rather than cutting out whole food groups.
If bloating is your main symptom, our guide to bloating after eating covers other common causes worth ruling out first.
Sources
This article is for general information only and isn't a substitute for advice from a doctor, dietitian or other qualified healthcare professional.