Symptoms of Food Intolerance You Should Be Aware Of | Sensitivity Check
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How do you know you have a food intolerance? It’s the symptoms, of course. However, unlike severe allergic reactions, where the symptoms occur rapidly and unmistakably, the symptoms of food intolerances are often more subtle. They gradually worsen for hours or days after consuming the trigger foods.

The problem? People can live with symptoms for years without ever drawing a connection with a particular foodstuff. Worse, they may not even realise they’re experiencing a symptom of food intolerance at all.

Below, we cover some common symptoms of food intolerance, linking them to the potential culprit behind the intolerance.


Bloating describes the feeling of fullness or swelling in the stomach after eating. There are several benign causes of bloating. For example, aerophagia (or swallowing air) is a common cause, as is drinking fizzy, carbonated beverages.

Nonetheless, the underlying cause is often a food intolerance. Usually, the mechanism involves the inability to digest a particular foodstuff. As a result, bacteria in your gut begin to ferment, producing carbon dioxide as a byproduct of digestion. Soon enough, you experience more bloating, more belching, more gas.

Lactose intolerance, in particular, commonly causes bloating, as the body cannot digest lactose, a sugar found in milk and dairy products.

Changes in Bowel Habit

Unsurprisingly, the digestive system is the first system affected by a food intolerance. Diarrhoea or constipation might be polar opposites, but they can stem from a similar cause.

Diarrhoea is a common side effect of bowel irritation. The usual speed of gut motility is put into overdrive as the bowel seeks to expel the irritant. Coeliac disease, for example, often causes diarrhoea, as the bowel begins to become highly inflamed due to the presence of gluten (found in wheat, barley, and rye).

Constipation, on the other hand, is a classic sign of irritable bowel syndrome (particularly if a person experiences sudden fluctuations between loose and hard stools). FODMAP intolerances are a significant problem in people with IBS. FODMAPs are a group of carbohydrates that irritate and aggravate the digestive tract. As a result, gut motility can slow down, leading to hard, unmoving stools.


Nausea, a common symptom of food intolerance, arises when the body struggles to digest certain foods, leading to discomfort. Individuals with fructose intolerance may feel nauseous after eating foods high in fructose, as improper absorption causes gut fermentation.

Similarly, lactose-intolerant people might experience nausea post-dairy consumption due to lactose fermentation in the digestive system. Reactions to food additives like MSG or artificial sweeteners can also induce nausea. Identifying the link between diet and symptoms is crucial; a food diary can help trace nausea back to specific dietary triggers.

If food intolerance is suspected, consultation with healthcare professionals is advised for appropriate dietary advice and testing to identify the source of intolerance.


After digestive symptoms, headaches are probably among the next most common symptoms of food intolerance. Headaches come in several different forms – that either indicate or dismiss the potential for a food intolerance.Symptoms of Food Intolerance You Should Be Aware Of

Deep aches in the temples or back of the head are indicative of a tension headache. This is a common sign of stress and tiredness. In contrast, food-related headaches are more generalised.

Some individuals may find that certain foods trigger a migraine. Migraines are mistakenly believed to be a really severe headache. Not so. Migraines are defined as a one-sided headache that pulses or throbs. Other symptoms like nausea, vomiting, sensitivity to light and sound, and visual auras often accompany it. It may last for hours or days.


Fatigue might sound like the least discomforting symptom. And that’s true to an extent. But it’s also the most insidious and hard to identify. What’s the difference between a poor night’s sleep and food-related fatigue?

Ask yourself: Am I tired all the time? When was the last time I felt truly rested? If it’s hard to answer the question, you could be experiencing fatigue due to food intolerance.

Of course, fatigue is a fairly vague symptom and is commonly associated with several conditions. Hypothyroidism (low levels of thyroid hormone), anaemia, and chronic diseases are other potential causes. But a food intolerance should also be considered among the culprits.

Fatigue is a natural side effect if your food is constantly causing a low-level state of inflammation (releasing certain hormones and chemicals into the bloodstream). Only by eliminating the trigger can your energy levels return to normal.

Skin Rashes

Skin rashes are another one of the symptoms of a food intolerance. Such rashes can appear as eczema, hives, or just general itchiness and inflammation of the skin. Look for redness, swelling, breaks in the skin, dryness, and other markings.

Unlike immediate allergic reactions that produce hives or anaphylaxis, food intolerance-related skin issues develop more slowly and can persist or recur over time.

When the body cannot properly digest or react adversely to certain foods, it can trigger a minor immune response. For example, gluten intolerance can lead to dermatitis herpetiformis. It’s not quite as bad as it sounds. Signs include itchy blisters and bumps, primarily on the elbows, knees, and buttocks.

Identify the Cause of Your Food Intolerance Symptoms

Do any of these symptoms of food intolerance sound familiar? If so, speak to your doctor to help identify the underlying cause. They can perform several blood tests and complete a medical history to determine if a severe problem is occurring.

In addition to a doctor’s visit, you should also perform a food sensitivity and intolerance test. Sensitivity Check’s Individual Ultimate Test is among the most comprehensive available tests. Identifying up to 975 items, the home-to-lab hair sample test only requires a small hair sample. You’ll receive your results back in less than a week via email or our app. These results detail the percentage likelihood of an intolerance.

Don’t let the symptoms of food intolerance dominate your life. Buy your Individual Ultimate Test and become symptom-free.

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This article was written by Joseph, our Health and Science Copywriter and Qualified Doctor

You can read more about them on their page.