Bloating after dairy, a rash after shellfish, tiredness after a heavy meal: it is natural to wonder whether a food is to blame. But “food allergy”, “food intolerance” and “food sensitivity” are not the same thing, and each needs a different approach and a different kind of test. Before you book a food sensitivity test, it helps to understand what each term means, how the tests work, and what results can and cannot tell you.
This guide is general information. If you have symptoms after eating, especially severe or sudden ones, speak to a doctor before changing your diet or relying on any test.
Intolerance vs allergy vs sensitivity
The three terms are often used interchangeably, but they describe different things.
Food allergy is a reaction of the immune system. In the most common type, the body produces an antibody called IgE against a food protein. When the food is eaten again, the immune system reacts, often within minutes to a couple of hours. Symptoms can include hives, swelling of the lips or face, itching, vomiting, wheezing or, in severe cases, anaphylaxis, which is a medical emergency. Common triggers include peanuts, tree nuts, milk, egg, wheat, soy, fish and shellfish.
Food intolerance does not involve the immune system in the same way. It usually happens because the body has difficulty digesting a food, for example due to a shortage of a digestive enzyme. Symptoms are mostly digestive, such as bloating, wind, stomach pain or diarrhoea. They tend to come on more gradually and often depend on how much of the food you eat. Intolerances can be uncomfortable but are not life-threatening.
Food sensitivity is a looser term. It is often used for symptoms that seem linked to a food but do not fit a clear allergy or intolerance. It is also the term many commercial tests use.
The key point: if you suspect a true food allergy, you need a medical allergy assessment, not an intolerance test.
Common intolerances, including dairy and lactose
Some of the more common food intolerances include:
- Lactose intolerance. Lactose is the natural sugar in milk. People with lactose intolerance produce less of the enzyme lactase, so undigested lactose reaches the gut and causes symptoms. It is very common worldwide and becomes more common with age.
- Fructose malabsorption. Difficulty absorbing fructose, a sugar found in fruit, honey and some sweeteners.
- Sensitivity to FODMAPs. FODMAPs are a group of fermentable carbohydrates found in foods such as onions, garlic, beans and some fruits. They can trigger symptoms in people with irritable bowel syndrome (IBS).
- Reactions to food additives, such as sulphites in some wines and dried fruit.
It is also important to know about coeliac disease. This is an autoimmune condition triggered by gluten, not an intolerance. It needs a specific medical diagnosis through blood tests and often a biopsy, and you should keep eating gluten until testing is complete.
A “milk problem” can be either lactose intolerance or a cow’s milk allergy, which are very different. A dairy intolerance test should be chosen with your doctor so that the right condition is being tested for.
How blood and at-home tests work
Different tests look for different things:
- Allergy blood tests (specific IgE). These measure IgE antibodies to particular foods. A doctor orders and interprets them alongside your symptoms.
- Skin prick tests. A small amount of food extract is placed on the skin, which is then lightly pricked. A raised bump can suggest sensitisation. These are done in a medical setting.
- Oral food challenge. Under close medical supervision, you eat gradually increasing amounts of a food. This is considered the most reliable way to confirm or rule out a food allergy.
- Lactose intolerance tests. A hydrogen breath test is commonly used, measuring gases produced when lactose is not digested.
- IgG food intolerance tests. Many commercial blood tests, including some at-home finger-prick kits, measure IgG antibodies to a large panel of foods.
If you are considering a food intolerance blood test that measures IgG, it is important to understand its limits, explained below.
What results mean and their limits
IgG test results are not a diagnosis of allergy or intolerance. Major allergy societies, including the European Academy of Allergy and Clinical Immunology (EAACI) and the American Academy of Allergy, Asthma and Immunology (AAAAI), advise against using IgG testing to diagnose food intolerance. IgG antibodies to foods are commonly found in healthy people and may simply reflect that you eat those foods regularly.
This matters because cutting out many foods based on an IgG result can lead to an unnecessarily restricted diet, with a risk of missing important nutrients, while the real cause of symptoms goes unfound.
Other tests have limits too:
- A positive allergy blood test or skin prick test shows sensitisation, but not always a true allergy. Results must be interpreted with your history.
- A negative result does not always rule out a problem.
- No test should be used to reintroduce a food you have reacted badly to without medical advice.
Often, the most useful approach is a detailed history with a doctor, a food and symptom diary, appropriate targeted tests, and, where suitable, a short, structured elimination and reintroduction plan guided by a doctor or registered dietitian.
When to see a doctor
Seek emergency care immediately if you or someone else has trouble breathing, swelling of the throat or tongue, a sudden drop in blood pressure, fainting, or widespread hives after eating.
Book a doctor’s appointment if you have:
- Any reaction that suggests allergy, even if it was mild
- Ongoing digestive symptoms, such as bloating, pain or changes in bowel habit
- Unexplained weight loss, blood in your stool, persistent vomiting or difficulty swallowing
- Symptoms in a child
- Plans to remove major food groups from your diet
Choosing the right test
The best test depends on what is happening and why. A doctor can help you decide whether you need an allergy assessment, a specific intolerance test such as a breath test, or a different investigation altogether. If you are considering a food intolerance test in Abu Dhabi or Dubai, discuss your symptoms with a doctor first so that any results can be interpreted properly.
FAQs
Can an intolerance test diagnose a food allergy? No. Food allergy needs a medical assessment, which may include IgE blood tests, skin prick tests or a supervised food challenge.
Are IgG food intolerance tests reliable? Major allergy societies advise against using IgG results to diagnose food intolerance, as IgG can be present in people without symptoms.
How is lactose intolerance tested? A hydrogen breath test is commonly used. A doctor may also suggest a supervised trial of reducing lactose.
Should I stop eating gluten before testing? No. If coeliac disease is being considered, keep eating gluten until testing is complete, unless your doctor advises otherwise.
Are at-home food allergy tests accurate? Home kits cannot replace a medical allergy assessment. Discuss any reaction with a doctor.
