Although the terms food sensitivity and intolerance are often used interchangeably, the body's reactions and the tests that measure these reactions are actually completely different. On one side is the digestive system's inability to break down a nutrient, on the other is the immune system waging a silent battle against that nutrient.
Let's examine the methods you can use to understand why your body reacts to which nutrient and the reliability of these tests more closely.
The Difference Between Food Intolerance and Sensitivity
Before moving to tests, we need to clarify what we are measuring. Food intolerance is usually when a nutrient cannot be digested due to enzyme deficiency (for example, lactose intolerance). Symptoms are usually limited to the digestive system.
Food sensitivity is an immune system response that is delayed but not as severe as an allergy. This reaction can sometimes appear 48 hours after eating, making it difficult to identify the responsible food.
Most Commonly Used Test Methods
There are several different methods currently used in clinics and home test kits to measure your body's reactions.
1. Breath Tests (For Intolerance)
Especially used to detect sugar intolerances (lactose, fructose) and excessive bacterial overgrowth in the small intestine (SIBO). A person consumes a specific sugar solution and then hydrogen or methane gas levels in their breath are measured at specific intervals. If your body cannot digest this sugar, bacteria in the intestine ferment it, producing gases that are reflected in your breath.
2. IgG Blood Tests (For Sensitivity)
The most popular but most controversial tests. They measure the level of IgG antibodies in your blood against specific foods. High IgG levels may indicate you consume that food very frequently or that your immune system has developed a defense against that food. These tests can provide you with a long "forbidden list," but results do not always replace clinical diagnosis.
3. Elimination Diet (Gold Standard)
Although not a test kit, it is considered the most reliable method in the medical world. Suspected foods are completely removed from the diet and whether symptoms improve is observed. Foods are then reintroduced one by one and your body's reaction is directly tested. No laboratory result is as clear as your body's own direct reaction.
What You Should Know About Test Reliability
Laboratory tests can sometimes be misleading. Experts are divided especially on IgG tests. Some studies suggest that high IgG levels actually indicate that "tolerance" to that food has developed (meaning your body recognizes that food). Therefore, rather than removing every food that appears in test results from your life, evaluating results with an expert and confirming with elimination diet is the healthiest approach.
Which Test is Right for You?
If you experience bloating and gas immediately after eating something, it may make sense to first measure your digestive capacity with breath tests. However, if you have systemic problems like chronic fatigue, migraines, or persistent skin rashes, an immune-focused screening and subsequently a professional elimination process will provide much more accurate results.
While being a detective of your own health, keeping a food diary rather than relying on a single test result will help you understand which food is truly "poison" and which is "medicine."
