7 Ways to tell if you have a food intolerance

Do certain foods disagree with you? Have you realised that it was not a one-time occurrence but rather a tendency or pattern of symptoms? Do you want to know the 7 ways to tell that you are intolerant to certain foods? Continue reading if you want to learn more or see our Food Intolerance Blood test.

Food intolerances vs. food allergies

Food intolerance and food allergies are often confused, but they’re actually quite different. While the symptoms can sometimes overlap, the causes behind them are not the same. Food allergies involve the immune system and can trigger immediate, sometimes severe reactions. In contrast, food intolerances are more likely to affect your digestive system and may not show up until hours—or even days—after eating the offending food. More people than ever suspect they have a food intolerance, yet many are left wondering if their daily discomfort is truly diet-related. With so many potential symptoms—bloating, fatigue, headaches, skin issues—it can be tricky to pinpoint what's really going on.

Food intolerance is more common than you might think, affecting up to 10% of people in Western countries. Despite this, many people continue their usual eating habits without knowing what's actually causing their symptoms. If you’re unsure whether your reactions are caused by an intolerance or an allergy, taking a test can offer clarity. The Combined Allergy & Intolerance Blood Test from Welzo is a great starting point—it screens for both food intolerances and allergic sensitivities in one easy-to-use kit. It’s a practical option if you suspect something in your diet is triggering symptoms but don’t know where to begin. For those specifically concerned about allergic reactions, the Allergy Testing Kit is another useful tool. It helps identify your body’s immune responses to a wide range of common allergens, giving you a clearer picture of what to avoid. Understanding the difference between a food intolerance and an allergy can help you make smarter choices—and feel better day to day. If you're frequently experiencing discomfort after eating, testing might be the first step to figuring out why.

• You often get migraines or headaches after eating specific foods

Monosodium Glutamate is the most well-known food chemical trigger (MSG). According to research, persons sensitive to dietary glutamate may develop headaches, muscular tightness, numbness or tingling, and weakness after consuming significant quantities. However, it may take many hours for symptoms to appear.

• If you cannot tolerate gluten products despite testing negative for Celiac Disease

Gluten is a protein found in wheat and several other grains that can cause digestive issues in certain individuals.

For those with coeliac disease, consuming gluten triggers an autoimmune reaction that damages the lining of the small intestine. This condition can be diagnosed through specific testing, such as the Coeliac Disease Test offered by Welzo, which helps identify whether your body is producing antibodies in response to gluten.

However, it's estimated that between 0.5% and 13% of people who don’t have coeliac disease still experience symptoms when eating gluten. This condition, often referred to as Non-Coeliac Gluten Sensitivity (NCGS) or Gluten Intolerance, causes symptoms that are very similar to coeliac disease—such as bloating, fatigue, and abdominal discomfort—but without the autoimmune response.

Interestingly, recent research suggests that individuals reacting negatively to gluten-containing foods without having coeliac disease might actually be sensitive to FODMAPs—fermentable carbohydrates also present in wheat and other grains. Exploring this possibility can offer further insight into what's truly behind your symptoms.

• If your Rheumatoid arthritis worsens

Another way to tell if you have a food intolerance is if you have Rheumatoid arthritis (RA) and it worsens. Unlike osteoarthritis, rheumatoid arthritis is not caused by normal wear and tear on the joints.

It is nearly always the result of genetics and environmental factors, including food. An immunological reaction to particular dietary compounds, similar to Hashimoto's and Celiac Disease, is considered to cause symptoms.

According to the theory, particular dietary sensitivities may trigger an inflammatory autoimmune reaction that lengthens or exacerbates the joint inflammation that causes swelling and pain in RA patients. It should be noted that this is simply a hypothesis that has not been disproven or verified.

Given that there is no known cure for RA and that the only dietary supplement that shows some (slim) promise is high-dose fish oil, removing the risk of food intolerance is a practical aspect of therapy.

• If you have widespread, persistent muscle or joint pain

Do you have long-term joint pain or muscle tenderness that interferes with your daily activities?

Fibromyalgia is a relatively recent medical disorder that affects up to 6% of the population, mostly middle-aged women. It is distinguished by long-term and widespread pain, not restricted to a single area.

According to research, over half of the patients with fibromyalgia reported that their symptoms worsened after consuming particular foods.

Identifying your food sensitivities and then limiting or eliminating those trigger foods may be the most significant thing you can do to address this disease.

• If you are constantly exhausted despite getting enough sleep

Do you get tired quickly? Not just physically but also psychologically and emotionally?

Chronic Fatigue Syndrome (CFS) is a condition marked by ongoing, often debilitating fatigue that doesn’t improve with rest. It can interfere significantly with daily life, making even basic tasks feel overwhelming. According to the NHS, CFS is more commonly diagnosed in women, especially between their mid-20s and mid-40s. If you're experiencing persistent tiredness and don't know why, it may be worth exploring potential underlying causes with a health check. The Tiredness and Fatigue Blood Test from Welzo can help identify issues such as vitamin deficiencies, thyroid problems, or other imbalances that could be contributing to your low energy levels.

Understanding the root cause of your fatigue is the first step toward feeling like yourself again.

• If you have an underactive Thyroid (Hypothyroidism)

An underactive thyroid (hypothyroidism) occurs when the thyroid gland in your body does not generate enough of the thyroid hormone.

Most hypothyroid instances are caused by Hashimoto's thyroiditis, an autoimmune condition. Preliminary research indicates a substantial relationship between Hashimoto's and gluten sensitivity (specifically celiac disease). Around 16% of Celiac Disease patients have antibodies that assault the thyroid.

Several studies have also shown that a gluten-free diet lowers the quantity of anti-thyroid antibodies, which is beneficial for hypothyroid therapy and avoiding future difficulties.

In other words, those who have an underactive thyroid are more likely to develop gluten sensitivity.

• If some foods cause rashes, eczema, or other skin issues

  

Because blood testing may provide an inaccurate diagnosis for allergies, we usually link skin responses with food allergies.

However, it is now generally established that food intolerances may also induce skin responses (such as eczema), but with a slower response than allergies.

Remember that most people with food intolerance can handle a decent quantity of the food's main ingredient, but symptoms may appear if they consume too much (or too often).

Salicylate, a natural dietary chemical, is one of the leading causes of skin disorders and histamine. It has been hypothesised that around 2.5 per cent of Europeans are sensitive to salicylates.

While it is almost impossible to eliminate all salicylates, reducing the quantity taken to a bearable level is the most efficient strategy to control it. Tomatoes and peppers (also known as capsicum or paprika) are two of the most prevalent sources of salicylates reported by patients.

Food intolerance may have significant consequences for your health and should be addressed carefully. Many individuals are intolerant or hypersensitive to certain foods and substances, such as gluten, caffeine, and dairy.

What are the best foods to eliminate?

It is usually helpful to start an elimination food program when you avoid foods which cause the most discomfort in the person. You may eliminate a single food at any given moment, or you could eliminate them all at once. Start at the food you notice makes you feel unwell or you think contributes to any of the symptoms mentioned above. Keeping a journal documenting which foods you have eliminated and how you feel, might assist you in this elimination process. This way you can document all the foods you have tested and won't lose track of which food to eliminate next. Welzo offers a selection of intolerance tests that can guide you toward the most likely culprits. These tests are designed to detect common food intolerances and can provide a useful starting point—especially if you’re feeling overwhelmed or unsure where to begin.This may even help you with meal planning! However, it may take a couple of days for your body to recover from the last time you ate that particular food. Therefore, patience is key.

Is there any food intolerance test?

Many firms have food intolerance testing equipment which is not scientifically proven and is not recommended by the British Dietarian Association. The most effective way to diagnose food intolerance is to check your symptoms. Watch what happens when we omit the foods and retake the foods from our diet once again.

Conclusion

If you do notice the abovementioned symptoms try cutting those foods out of your diet and discover if it makes a difference. Alternatively, if you are worried about your symptoms or they increase in severity, talk to your doctor or a nutritionist about testing and treatment choices. Although food intolerances are typically less severe than food allergies, they may nevertheless have an impact on your quality of life. That is why it's critical to try to discover food intolerances to avoid unpleasant symptoms and health problems.