The tell-tale signs of popular food intolerances, according to a nutritionist

Skin problem food intolerance. (Getty Images)
Your symptoms could be telling you you have a food intolerance. (Getty Images)

Food intolerances – when your body isn't able to digest a certain food or ingredient – are common. But not all of us realise which symptoms might be a sign of one, or put off actually figuring it out.

So, if you've been experiencing uncomfortability, digestive issues and a whole host of other symptoms you think could be related to what you're eating, take this as your reminder to finally take that first step towards getting to the bottom of it.

"Symptoms of food intolerances are specific to each individual and can vary in severity from person to person. However, they most commonly involve the digestive system, the respiratory system, and the skin," says nutritionist Shona Wilkinson.

"Most people also assume that symptoms of an intolerance start to show up immediately after consumption – this is wrong! In some cases, symptoms of an intolerance have even been shown to arise 48 hours after consumption."

Here the expert runs through the most common foods you might be intolerant to and the tell-tale signs, plus what to do if you think you do have an intolerance to something.


Variety of Breads and pastas
Gluten is a protein found in things like wheat, rye and barley. (Getty Images)

"Gluten has certainly become the thing to avoid for many in recent years, with over one in ten people now steering clear due to its association with symptoms such as bloating, poor digestion, and IBS. While not as severe as celiac disease, a gluten intolerance can still significantly impact an individual's quality of life," says Wilkinson, lead nutritionist at ethical supplement brand DR.VEGAN.

Here are some of the common signs she says to look out for if you think you could be intolerant to gluten:

  • Poor digestion and stomach issues: Poor digestion is a very common symptom of a gluten intolerance and includes things like excess bloating, constipation, gas, abdominal pain, and diarrhoea. These symptoms typically occur shortly after eating gluten-heavy foods such as bread, pasta, and cereals

  • Fatigue: An intolerance to gluten can also leave your insides struggling to absorb all the nutrients they need, leaving you feeling like you have no energy throughout the day. This, combined with consistent abdominal pain, disrupted sleep, and general inflammation of the stomach can lead to chronic fatigue

  • Brain fog: An intolerance to gluten can leave you experiencing brain fog, characterised by difficulty concentrating, issues with memory, and feelings of general fogginess. This is caused when the brain is ‘starved’ of key nutrients due to damage within the intestinal lining, meaning it’s unable to act in the way it needs to in order to help you feel ‘on the ball’ throughout the day

  • Swelling or itching of the throat: If your intolerance to gluten extends into the realms of a wheat allergy, you may also experience a swelling or itching of the throat following consumption, typical of an allergic response. In this case, it’s worth seeking medical help immediately after to help manage your allergic reaction

Belly ache
Don't just put up with possible food intolerance symptoms. (Getty Images)

It is worth noting that a gluten intolerance and coeliac disease are separate things. Coeliac is an autoimmune condition where the body's immune system mistakenly attacks its own tissues when you eat gluten, damaging the lining of the small intestine and preventing the body from absorbing nutrients properly. If you are confirmed not to have coeliac disease but still have symptoms, you could have a gluten intolerance.


Cropped shot of young Asian woman with a shopping cart, shopping in the dairy section of a supermarket. She is reading the nutrition label on the package of a fresh organic cheese
Could something in your diet be causing your symptoms? (Getty Images)

"Signs of dairy intolerance, also known as lactose intolerance or dairy sensitivity, can vary from mild to severe and typically manifest after consuming dairy products," says Wilkinson. These, she explains, include:

  • Digestive issues: One of the most prominent signs of dairy intolerance is digestive discomfort. Symptoms may include bloating, abdominal pain, cramps, diarrhoea, or nausea. These symptoms occur due to the inability to properly digest lactose, the sugar found in dairy products, leading to fermentation by gut bacteria and subsequent digestive trouble

  • Increased gas: When lactose remains undigested in the intestines, it’s fermented by bacteria in the gut and gas is produced as a byproduct. If you find yourself feeling particularly gassy after consuming dairy, it may be that you’re intolerant…

  • Skin problems: A dairy intolerance can also manifest itself in the skin, leading to conditions such as eczema, acne, or dermatitis. In others, consuming dairy may trigger an allergic response, leading to immediate inflammation, rashes, or general irritation

  • Nausea: A study revealed that nausea was the second most common symptom associated with a lactose intolerance in children, after abdominal pain. When lactose ferments in the gut, the resulting gas can leave you feeling sick, often leading to vomiting

Man looks at the flaky skin on his hands with eczema, psoriasis and other skin diseases such as fungus, plaque, rash and spots. Autoimmune genetic disease.
If you have a food intolerance, eliminating it from your diet with advice from a professional could help ease symptoms. (Getty Images)

Unlike gluten in coeliac disease, lactose does not damage your body, you just may get these symptoms from not digesting it properly.

Other intolerances and allergies

Shot of a young businesswoman having coffee and using a smartphone in a modern office
There are some lesser known intolerances to ingredients too. (Getty Images)

"Though intolerances to gluten and dairy are amongst the most common out there, there are certainly some other intolerances and potential allergies you should be aware of," Wilkinson points out.

"This includes a sensitivity to caffeine, which tends to be determined by genetics and can manifest itself in the form of a rapid heart-rate, insomnia, and general restlessness. This also includes an intolerance to salicylates, found in fruits, vegetables, spices and teas, and an allergy to histamines, which can often trigger the body’s immune response.

What to do if you think you have a food intolerance

Doctor discussing with man over digital tablet. Young male is visiting healthcare worker in clinic. They are sitting at desk.
Always consult a professional about symptoms. (Getty Images)

"If you suspect you have a food intolerance, it’s essential that you take proactive steps to identify and manage it effectively," says Wilkinson. Here are top steps you might want to follow to help identify and tackle the problem:

  • Keep a food diary: Start by keeping a detailed food diary of what you’re eating and any symptoms you may be experiencing. Once you start noticing a pattern between what you’re eating and how your body reacts, you should be able to identify what it is that’s wreaking havoc on your insides

  • Eliminate certain foods: Once you’ve identified any problematic foods or ingredients, eliminate them from your diet for up to four weeks to see if symptoms improve. If they don’t, gradually reintroduce these into your diet before deciding what to eliminate next

  • Consider testing: If symptoms continue, consider contacting a medical professional who can recommend specific tests that are able to rule out certain intolerances

  • Take good care of your gut: Having a healthy gut microbiome will help combat the symptoms such as diarrhoea, stomach pain, gas, and bloating where possible, so try eating gut-friendly foods such as kimchi and sauerkraut, or incorporate a daily supplement into your diet [if safe and right for you]

What is the difference between food intolerances and IBS?

"IBS is a chronic gastrointestinal disorder, meaning the function of the gastrointestinal tract is disturbed. This means things like intestinal movement is sometimes disrupted and digestion is often impacted leading to pain, bloating, diarrhoea and gas," explains Wilkinson.

"Similarly, a food intolerance affects the digestive system, meaning it can’t break down certain foods. This comes from either a lack of or absence of certain digestive enzymes, meaning the food often ferments as it travels slowly through the intestines.

"Of course, the symptoms of the two are incredibly similar, and IBS often involves the presence of a food intolerance, though not exclusively. In DR.VEGAN’s research, they found that gut health can be massively impacted by diet, with refined bread and alcohol being the main culprits when it comes to bringing about digestive discomfort.

"The reality is, however, the two often go hand-in-hand and are important to keep on top of in order to combat the symptoms of both where possible."

Many of the symptoms mentioned can be a sign of many different things, so you should always consult your doctor who can advise what the best next steps are. Also consult a healthcare professional before changing or eliminating anything from your diet.