Food Intolerance Test: Allergy, Intolerance, Sensitivity and Which Test Suits Each

In short: Food allergy, intolerance and sensitivity are different problems, so no single test covers all three. For suspected IgE-mediated food allergy (driven by the antibody IgE), assessment starts with your history and selected skin-prick and/or specific IgE tests. Some food allergies involve other immune pathways and need different assessment. A hydrogen breath test assesses lactose malabsorption; associated symptoms help establish intolerance. Allergy societies do not recommend IgG panels for diagnosis. A doctor interprets results alongside your history; elimination diets are used when appropriate.

What is the difference between food allergy, intolerance and sensitivity?

A food allergy involves the immune system, a food intolerance usually involves digestion, and "food sensitivity" is a loose term with no single agreed meaning.

• Food allergy. The immune system reacts to a food protein, often through an antibody called immunoglobulin E (IgE). Symptoms such as hives, swelling or vomiting usually start soon after eating. A reaction can be severe, even with small amounts.

• Food intolerance. The body has trouble digesting a food. Lactose intolerance is the common example: too little of the enzyme lactase means milk sugar reaches the large bowel, causing bloating, pain or loose stools. It is uncomfortable but is not an allergy.

• Food sensitivity. People use this word for symptoms that seem to follow a food, such as gut discomfort or skin flares, when allergy and intolerance do not explain them. Because the term is loose, it pays to ask what a "sensitivity test" is actually measuring.

Coeliac disease is separate again. It is a permanent immune reaction to gluten, the protein in wheat, barley and rye, and it needs its own tests.

Which test is used for a food allergy?

For suspected IgE-mediated food allergy, assessment starts with your history and selected skin-prick and/or specific IgE tests. Some food allergies involve other immune pathways and need different assessment. Guidelines from the European Academy of Allergy and Clinical Immunology (EAACI) describe these assessment options:

1. An allergy-focused history. What you ate, how soon symptoms began, and what happened.

2. Skin prick test. A tiny amount of food extract is placed on the skin and pricked to look for a small raised reaction.

3. Specific IgE blood test. This measures IgE against a particular food.

4. Oral food challenge. The suspected food is eaten in measured amounts under medical supervision. EAACI calls this the reference standard, and it is used when other results are unclear.

These tests work better for some foods than others. They support a diagnosis well for peanut and cashew, but perform less well for foods such as wheat and soya. A positive skin or IgE result shows sensitisation, meaning the immune system has noticed the food. It is the history, or a challenge, that shows whether the food really causes a reaction.

How is lactose intolerance tested?

The usual test is a hydrogen breath test, which assesses lactose malabsorption (poor absorption of milk sugar). Associated symptoms help establish intolerance. You drink a measured dose of lactose, and breath samples are taken over the next few hours. Undigested lactose is fermented by bowel bacteria, which release hydrogen that you breathe out.

A North American expert consensus uses a 25 g lactose dose and treats a rise in hydrogen of 20 parts per million or more from the baseline as positive. It also advises excluding bacterial overgrowth in the small bowel first, to avoid false positive results. A lactose tolerance blood test can assess malabsorption. Genetic testing cannot establish symptoms or detect secondary lactase deficiency; suitability depends on ancestry and the variants tested.

A positive result is common in India and does not always mean you must give up milk. In a study of 153 healthy Indian volunteers, the breath test was abnormal in about 79% of southern and 57% of northern participants. Far fewer had symptoms after the test dose. A review in Gut notes that most people with lactose malabsorption tolerate at least 12 g of lactose, about 250 mL of milk.

Which tests check for coeliac disease?

Coeliac disease is first checked with a blood test for specific antibodies, such as tissue transglutaminase. A biopsy of the small bowel, taken during an endoscopy, confirms the diagnosis in most adults.

Do not go gluten-free before testing. A European guideline states that blood tests and biopsy should be done while you are still eating gluten.

What can IgG food panels show, and what are their limits?

Food-specific IgG mainly shows that your body has met a food, and allergy societies do not recommend it for diagnosing food allergy or intolerance. These panels measure IgG antibodies, or a subtype called IgG4, against many foods at once.

The published positions are clear:

• EAACI (2008) says IgG4 to foods reflects a normal immune response after eating those foods, and does not indicate imminent allergy or intolerance. It advises against this testing for food-related complaints.

• The Canadian Society of Allergy and Clinical Immunology (2012) says positive results are to be expected in healthy adults, and discourages the testing for identifying or predicting adverse reactions to food. It records that the American Academy of Allergy, Asthma and Immunology also supports the EAACI view.

Two practical risks follow. Long lists of "positive" foods can lead to unnecessary restrictions. And a person with a true IgE allergy may not have raised IgG to that food, so a "negative" panel must never be used as a reason to eat a food that caused a reaction.

Immune tests for foods differ in what they measure, so ask which antibody a test looks at, and how your doctor will use the answer.

What is a supervised elimination diet?

A supervised elimination diet means removing suspected foods for a limited time, watching your symptoms, and then bringing each food back one at a time with a doctor's guidance. It tests the result against what your body actually does.

• Keep a diary first. Note meals, timing and symptoms, including skin and gut changes.

• Remove only what your history or tests point to. Long restrictions can cost you nutrition and quality of life.

• Reintroduce one food at a time. If symptoms return with one food and not another, that is useful evidence.

• Do not self-test dangerous foods. Never reintroduce a food at home if it has caused swelling, breathing trouble or faintness. That needs medical supervision.

Trouble breathing, swelling of the lips or throat, or faintness after eating is an emergency. Use your prescribed adrenaline auto-injector immediately if available, and call 112 for an ambulance. Do not stand or walk.

How does a SOMA doctor decide which test is right for you?

At SOMA, a doctor looks at your history, symptoms and earlier reports before suggesting any test. Bloating, skin problems and tiredness can have many causes, so food is one question among several.

SOMA's How We Do It page lists food sensitivity and allergy testing, which measures immune responses to specific foods. It may be relevant for people with digestive issues, eczema, or symptoms that follow meals. What a result means depends on the test and your clinical history, so your doctor reads it alongside both.

SOMA centres in Mumbai and New Delhi

SOMA doctors see patients at two centres:

• Mumbai: A-507, Kohinoor Square, N.C. Kelkar Marg, Shivaji Park, Dadar West, Mumbai 400028. Phone +91 98671 94033.

• New Delhi: E-354, Greater Kailash II, New Delhi 110048, serving Delhi NCR and Gurugram. Phone +91 87969 92001. More about the New Delhi centre.

The New Delhi centre is independently operated under licence from SOMA Longevity Sciences, and its own doctors lead care there. Both centres follow the same SOMA assessment and diagnostic standards. Online consultations are also available. Contact either centre.

Questions people ask

What is a food intolerance test?

It depends on the food. Lactose intolerance is usually checked with a hydrogen breath test. For some suspected food reactions, supervised elimination and reintroduction can help assess symptoms after appropriate investigation.

What is the difference between a food allergy test and a food sensitivity test?

For suspected IgE-mediated food allergy, assessment starts with your history and selected skin-prick and/or specific IgE tests. Some food allergies involve other immune pathways and need different assessment. "Sensitivity test" is a loose term that can mean different things, so ask what is being measured and how the result will be used.

Are IgG food intolerance tests reliable?

Allergy societies in Europe and Canada do not recommend food-specific IgG for diagnosing allergy or intolerance. They note that positive results are expected in healthy adults, because IgG mainly reflects having eaten a food.

How do I test for lactose intolerance?

A hydrogen breath test assesses lactose malabsorption, by measuring hydrogen in your breath after a measured dose of lactose. Associated symptoms help establish intolerance. A doctor can arrange the test and explain the result. A positive result does not always mean giving up milk, as many people tolerate smaller amounts.

Where can I get a food intolerance test in Mumbai or Delhi?

Start with a doctor who can match the test to your symptoms. Doctors at SOMA's centres in Dadar West, Mumbai and Greater Kailash II, New Delhi review your history, advise which tests make sense, and read the results with you.

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