Intolerance test

Food Intolerance Test: Comprehensive Guide to Understanding, Performing and Interpreting Your Results

The food intolerance test is a procedure increasingly sought by people who suffer from diffuse or recurring symptoms: persistent digestive problems, chronic fatigue, frequent headaches, skin discomfort or even unexplained joint pain.

These symptoms, often subtle and delayed, can considerably affect your quality of life without you being able to clearly identify the cause. The intolerance test presents itself as a solution to identify foods or substances likely to provoke these adverse reactions.

In this comprehensive guide, you'll discover everything you need to know about intolerance testing: how it works, the different methods available, how to interpret your results and how to use it to improve your daily well-being.

Intolerance Test

What is a food intolerance?

A food intolerance is a reaction of the body to certain foods, ingredients or substances, generally not related to the immune system. Unlike allergies, intolerances are often caused by:

• Digestive difficulty: the body struggles to digest certain food components

• Enzyme deficiency: absence or insufficiency of enzymes necessary for digestion (such as lactase for lactose)

• Increased sensitivity to certain chemical components present in foods

• Poor intestinal absorption of certain substances

Typical symptoms of an intolerance

Food intolerances manifest through varied symptoms, often delayed by several hours to several days after consumption, which makes their identification difficult:

Digestive symptoms:

• Bloating and gas

• Diarrhoea or constipation

• Abdominal pain

• Nausea

• Gastric reflux

General symptoms:

• Chronic fatigue

• Headaches or migraines

• Concentration difficulties

• Joint or muscle pain

Skin symptoms:

• Skin rashes

• Eczema or psoriasis

• Itching

• Redness

These symptoms can be mild to moderate and develop gradually, which explains why many people live with them for years without identifying the cause.

What is the difference between an intolerance and a food allergy?

It's essential to clearly distinguish these two reactions, as their mechanism, severity and management are totally different.

Food allergy

A food allergy involves an immune system reaction, particularly through the production of immunoglobulin E (IgE). This reaction can be:

• Immediate: occurs within minutes or hours following ingestion

• Potentially serious: can lead to anaphylactic shock, Quincke's oedema or breathing difficulties

• Requires strict avoidance: even small quantities can trigger a reaction

• Easily identifiable: symptoms appear rapidly after consumption

Food intolerance

A food intolerance generally doesn't involve the immune system in the same way. It is characterised by:

• Delayed symptoms: can appear several hours or days after ingestion

• Lesser severity: uncomfortable but rarely dangerous

• Variable tolerance: small quantities can sometimes be tolerated

• Difficult identification: as symptoms are delayed, it's complex to make the link with the responsible food

Important: If you present significant or sudden symptoms after eating a food, consult a healthcare professional immediately. This may be a food allergy requiring urgent medical care.

How does a food intolerance test work?

The objective of an intolerance test is to identify elements likely to provoke adverse reactions in your body. Several analysis methods exist, each with its own logic and advantages.

1. IgG tests (blood analysis)

This method measures levels of immunoglobulin G (IgG) specific to different foods in your blood. The principle is based on the hypothesis that a high level of IgG against a particular food may reflect sensitivity or a low-grade inflammatory reaction.

How it works:

• A blood sample is collected (generally by finger prick)

• Blood is analysed in the laboratory to measure IgG antibodies against several hundred foods

• Results indicate foods for which your body produces the most antibodies

Important point: It's recommended to regularly consume the foods to be tested in the weeks preceding collection to ensure antibody detection. IgG interpretation must be cautious and ideally performed with a healthcare professional to avoid unnecessary dietary restrictions.

2. Hydrogen breath tests

These tests are particularly used to diagnose specific intolerances such as those to lactose or fructose. They are considered reliable and are often used in medical settings.

The principle:

• A fasting period is necessary before the test

• You ingest a controlled dose of the suspected food (lactose, fructose, etc.)

• Exhaled air is measured at regular intervals (every 15 to 30 minutes for 2 to 3 hours)

• A significant increase in hydrogen in exhaled air indicates poor absorption

This increase in hydrogen is due to fermentation of the undigested food by intestinal bacteria, which produces hydrogen that passes into the blood then is exhaled through the lungs.

3. Tests by hair analysis

This method uses a hair sample collected at the root, which is then analysed in the laboratory. It is presented as simple, quick and non-invasive.

How to proceed:

• Collect a few strands of hair (3 to 4 strands) at the root

• Hair must measure at least 1 cm in length

• Ideally collect hair with root (pulled hair) rather than cut

• If you use cut hair, cut it as close as possible to the root

• Avoid using hair from a brush to avoid contamination

All hair types can be tested, and cosmetic treatments (dyeing, bleaching, perming) don't affect results.

The laboratory then analyses the sample according to different techniques (spectrometry, spectroscopy, chemical reactions) to identify food and non-food substances likely to provoke a reaction.

4. Other analysis methods

Some laboratories use complementary methods:

• IgE antibody test: used primarily to detect allergies, but can reveal certain sensitivities

• Complement test: measures levels of immune system proteins to identify sensitivity reactions

• Skin reaction test: food extracts are applied to skin to observe possible reactions

Which elements can be detected by an intolerance test?

Modern intolerance tests aren't limited to foods. They can identify sensitivities to a wide range of elements present in your daily environment.

Foods tested

Intolerance tests generally analyse several hundred common foods:

• Dairy products: cow's milk, cheeses, yoghurts, butter

• Cereals: wheat, rye, barley (gluten), maize, rice, oats

• Animal proteins: beef, chicken, pork, fish, seafood, eggs

• Fruits: apples, bananas, citrus fruits, berries, nuts

• Vegetables: tomatoes, peppers, aubergines, cruciferous vegetables, legumes

• Nuts and seeds: almonds, walnuts, hazelnuts, sunflower seeds

• Spices and herbs: pepper, cinnamon, ginger, basil, parsley

Additives and food preservatives

Tests can detect sensitivities to common additives:

• Food colourings (E100 to E199)

• Preservatives (E200 to E299): benzoates, sulphites, nitrates

• Antioxidants (E300 to E399)

• Emulsifiers and stabilisers (E400 to E499)

• Flavour enhancers (E600 to E699): monosodium glutamate (MSG)

• Artificial sweeteners: aspartame, sucralose, saccharin

Non-food elements

Beyond food, intolerance tests can identify sensitivities to:

Environmental allergens:

• Pollens (trees, grasses, herbaceous plants)

• Mites and household dust

• Moulds and spores

• Animal hair and dander

Chemicals:

• Household and industrial products

• Solvents and detergents

• Cosmetic and personal hygiene products

• Perfumes and fragrances

Textiles and materials:

• Certain fabrics (latex, elastane)

• Textile dyes

• Building materials

Heavy metals:

• Lead, mercury, arsenic, cadmium

• Toxic accumulation in body tissues

This capacity to detect non-food elements is particularly useful for identifying causes of non-specific symptoms such as skin irritations, respiratory problems or unexplained chronic fatigue.

How is an intolerance test performed? (Complete procedure)

The procedure varies according to the type of test chosen. Here are the detailed steps for each method.

For an IgG test (blood collection)

Before the test:

• Regularly consume the foods you wish to test in the 2 to 4 weeks preceding collection

• This step is important so your body produces detectable antibodies

On the day of collection:

• Blood collection by finger prick (a few drops suffice)

• Sample is placed on special blotting paper

• You return the sample to the laboratory in the envelope provided

Laboratory analysis:

• Blood is analysed to measure IgG levels against several hundred foods

• Results are generally available within 7 to 14 working days

For a hydrogen breath test

Before the test:

• Fast for 8 to 12 hours

• Avoid certain foods the day before (according to laboratory instructions)

During the test:

• You breathe into a device to measure your baseline hydrogen level

• You ingest a controlled dose of the suspected food (lactose, fructose, etc.)

• You breathe into the device at regular intervals for 2 to 3 hours

Results:

• A significant increase in hydrogen indicates probable intolerance

• Results are generally interpreted immediately

For a test by hair analysis

Test ordering:

1. Select your test online

2. Order and pay online

3. Receive your home collection kit with your personalised instructions

Sample collection:

• Collect 3 to 4 strands of hair at the root

• Minimum length: 1 cm

• Place sample in the resealable bag provided

• Important: Don't use metal packaging (aluminium) for dispatch

Dispatch and analysis:

• Return sample to laboratory in pre-stamped envelope

• Laboratory performs analysis

• You receive your results by email within 7 to 14 working days

How to interpret intolerance test results?

Interpreting results depends on the type of test performed. Here's how to read and understand your results for each method.

IgG test results

Results are generally presented as a table or graph indicating the IgG antibody level for each food tested. The usual classification is:

Reaction level:

• High reaction (or severe): avoidance recommended for 3 to 6 months

• Moderate reaction: consumption limitation recommended

• Mild reaction: food rotation possible (consume moderately and spaced out)

• No reaction: normal consumption possible

Point of attention: High IgG levels may simply indicate frequent exposure to a food without necessarily signifying intolerance. This is why it's essential to be accompanied by a healthcare professional to avoid overly broad food exclusions that could lead to nutritional deficiencies.

Breath test results

Results are more direct and objective:

• Negative test: no significant increase in hydrogen → no intolerance detected

• Positive test: increase in hydrogen beyond threshold → probable intolerance

These tests are particularly reliable for lactose and fructose intolerances, as they directly measure your body's capacity to digest these substances.

Hair test results

The report generally presents you with:

Classification of tested elements:

• Sensitive Reaction: elements for which the test shows proven sensitivity

• Mild Reaction: elements for which you could potentially have sensitivity

• No Reaction: elements for which the test shows no sensitivity

Recommended action plan:

• Focus first on elements in "Sensitive Reaction"

• Implement temporary avoidance of these elements for 4 to 6 weeks

• Observe evolution of your symptoms

• Progressively reintroduce elements to confirm their impact

What precisely do your results contain?

Whatever the test type, you'll generally receive:

A detailed report comprising:

• Complete list of tested elements with their reaction level

• Classification by categories (dairy products, cereals, fruits, vegetables, etc.)

• Summary of main sensitivities detected

• Detailed explanations to understand your results

Personalised recommendations:

• Foods to temporarily avoid

• Foods to limit or consume in rotation

• Advice for adapting your diet without creating deficiencies

• Substitute food suggestions

Practical advice:

• How to read food labels

• How to plan your meals

• Recipes adapted to your sensitivities

• Support for the reintroduction phase

Are there alternatives to intolerance tests?

Yes, the most reliable and personalised method remains the elimination-reintroduction protocol, often recommended by healthcare professionals.

The elimination-reintroduction diet

This method, whilst longer, allows your intolerances to be identified precisely and personally, without high cost.

Phase 1: Elimination (4 to 6 weeks)

• Temporarily remove suspected foods from your diet

• Keep a detailed food diary

• Note the evolution of your symptoms day by day

Phase 2: Reintroduction (several weeks)

• Reintroduce foods one by one, at 3-4 day intervals

• Start with small quantities

• Carefully observe your body's reactions

• Note all symptoms in the 48 hours following reintroduction

Phase 3: Analysis and adaptation

• Clearly identify foods that trigger symptoms

• Adapt your diet accordingly

• Re-evaluate periodically (some intolerances can evolve)

This approach has several advantages:

• Personalised: it identifies what actually triggers YOUR symptoms

• Reliable: it establishes a direct cause-and-effect link

• Economical: no expensive testing necessary

• Educational: you learn to know your body and its reactions

Understanding certain concepts related to intolerances

To better understand your results and their impact on your health, here are some important notions.

What is food sensitivity?

Food sensitivity occurs when your body has difficulty digesting a particular food. Unlike an allergy, it doesn't involve an immediate and serious immune reaction.

Typical symptoms:

• Bloating and digestive discomfort

• Changes in bowel transit

• Headaches or migraines

• Chronic fatigue

• Concentration difficulties

Food sensitivity can also contribute to symptoms of chronic disorders such as irritable bowel syndrome, chronic fatigue, arthritis or certain neurological disorders.

What is non-food sensitivity?

Non-food elements can provoke reactions similar to those caused by foods:

• Recurring headaches

• Persistent fatigue

• Skin irritations

• Mild respiratory problems

• Diffuse inflammatory symptoms

Important: If you suspect an environmental allergy (pollen, mites, moulds), consult your doctor for specific allergy tests. Known allergies may or may not be detected in an intolerance test.

The importance of hormonal balance

Hormonal imbalance is one of the most common causes of general malaise. Numerous factors can affect your hormonal health:

• Unsuitable diet

• Chronic stress

• Poor intestinal health

• Weakened immune system

• Sedentary lifestyle

• Genetic factors

• Exposure to endocrine disruptors

Untreated food intolerances can contribute to disrupting your hormonal balance, causing symptoms such as menstrual cycle disorders, endometriosis, fertility problems or low testosterone.

The role of the intestinal microbiome

Your intestinal microbiome refers to all the good bacteria present in your digestive tract.

These bacteria play a crucial role for your health:

• They influence your digestion and metabolism

• They participate in synthesis of certain vitamins

• They modulate your immune system

• They can minimise certain diseases

Unidentified food intolerances can disrupt your microbiome, creating a vicious circle of digestive symptoms and malabsorption.

Heavy metal toxicity

Metal toxicity corresponds to accumulation of large quantities of heavy metals in your body tissues. Those most concerned are:

• Lead: exposure via old paints, contaminated water

• Mercury: contaminated fish, dental amalgams

• Arsenic: contaminated water, pesticides

• Cadmium: smoking, certain contaminated foods

Variable symptoms according to metal: fatigue, cognitive problems, pain, digestive problems. Some advanced intolerance tests can include screening for these metals.

Food additives and their impact

Additives are substances added to foods to:

• Improve appearance or taste

• Preserve foods and extend their shelf life

• Facilitate industrial processing

• Stabilise products and make them safe for consumption

Main additive types:

• Colourings (E100 to E199)

• Preservatives (E200 to E299)

• Antioxidants (E300 to E399)

• Emulsifiers and stabilisers (E400 to E499)

• Flavour enhancers (E600 to E699)

They can be natural, synthetic identical to natural, or artificial. Many people develop sensitivities to certain additives, hence the interest in including them in intolerance tests.

Vitamin and mineral levels

Low vitamin levels occur when:

• Dietary intake is insufficient

• Your body has difficulty efficiently absorbing nutrients

• Your needs are increased (stress, activity, life stage)

• You take certain medications that interfere with absorption

Food intolerances can lead to chronic malabsorption, leading to nutritional deficiencies even if your diet seems balanced. This is why it's important to work with a nutritionist when implementing an elimination diet.

Who can take an intolerance test? (Important precautions)

The food intolerance test can be performed by the majority of adults in general good health. However, certain precautions must be taken.

People who can perform the test

• Adults presenting recurring digestive symptoms

• People suffering from unexplained chronic fatigue

• Individuals with persistent skin problems

• People with frequent headaches or migraines

• Healthy adults wishing to optimise their diet

Situations requiring prior medical advice

The test is not recommended without medical consultation for:

• Children under 2 years: their digestive system is still developing

• Pregnant or breastfeeding women: dietary restrictions can affect baby development

• People with immune disorders: autoimmune diseases, immunodeficiency

• People with serious pathologies: cancers, chronic inflammatory bowel diseases

• Individuals following heavy medical treatment: dietary restrictions may interfere

• People suffering from eating disorders: risk of aggravating restrictions

Important: An intolerance test never replaces medical consultation. If your symptoms are severe, worsening or if you have doubts, consult a healthcare professional before performing a test.

How to order your intolerance test?

Ordering an intolerance test is simple and can be done entirely online. Here are the detailed process steps.

Order steps

1. Select your test

• Choose the test type suited to your needs (complete IgG, breath test, hair analysis)

• Check the number of elements tested (some tests analyse 200 elements, others up to 600)

2. Order online

• Complete the order form

• Make secure payment

• Receive your confirmation by email with your customer code

3. Receipt of collection kit

• You receive your kit at home within a few days

• Kit contains everything necessary: collection material, detailed instructions, return envelope

4. Perform collection

• Carefully follow the instructions provided

• Collection takes only a few minutes

• No particular skills required

5. Return sample

• Place your sample in the pre-stamped return envelope

• Post it in any post box

• No additional postage costs

6. Receive your results

• Results sent by email within 7 to 14 working days after receipt of your sample at the laboratory

• Access to a secure online portal to consult and download your complete report

• Customer support available to answer your questions about your results

Processing times

Times vary slightly according to laboratory and test type:

• Standard IgG tests: 7 to 10 working days

• Complete tests (over 400 elements): 10 to 14 working days

• Breath tests: immediate results or within 24 hours

• Hair tests: 7 to 14 working days

You'll be notified by email as soon as your results are available.

Complementary tests to optimise your health

Beyond the intolerance test, other analyses can help you better understand your body's specific needs.

DNA nutrition test

Discover how your genetic heritage influences your metabolism and nutritional needs. This test analyses your genes to identify:

• Your capacity to metabolise certain nutrients

• Your specific needs for vitamins and minerals

• Your genetic sensitivity to gluten, lactose, caffeine

• Your metabolic profile (tendency to store fats, sensitivity to carbohydrates)

• Types of exercise most suited to your genetics

This test helps you personalise your diet according to your genes to optimise your well-

being, energy and body composition.

Coeliac disease test

If you think you're sensitive to gluten, our specific test for coeliac disease allows you to rapidly identify a genetic predisposition to this autoimmune condition.

Why it's important:

• Coeliac disease requires strict and permanent gluten avoidance

• It can cause serious intestinal damage if untreated

• A genetic diagnosis allows direction towards complementary examinations if necessary

This test is particularly recommended if you have family history of coeliac disease or if you present persistent symptoms despite a varied diet.

In summary: why take an intolerance test?

The food intolerance test can be a valuable tool to improve your quality of life if you suffer from unexplained chronic symptoms. Here's what it can bring you:

Clearly identify foods or substances that pose problems for you, rather than guessing or randomly eliminating entire food groups.

Reduce your symptoms by adapting your diet in a targeted and personalised manner.

Improve your digestion, energy, concentration and general well-being by eliminating sources of chronic inflammation.

Prevent deficiencies by working with a professional to adapt your diet whilst maintaining optimal nutritional balance.

Understand your body and its reactions to make informed dietary choices on a daily basis.

Our final recommendations

• Consult a professional: work with a nutritionist or dietitian to interpret your results and implement a suitable dietary plan

• Be patient: improvements can take several weeks after avoidance of problematic foods

• Keep a journal: note your symptoms and diet to identify cause-and-effect links

• Re-evaluate regularly: some intolerances can evolve over time, particularly after a period of intestinal healing

• Don't isolate yourself: adapt your diet without renouncing your social life

The intolerance test is a starting point to better understand your body and optimise your health. Use it as an exploration tool, complementing professional support suited to your personal situation.