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  • Writer's pictureRuth Hull

Why do I bloat after eating? Do I have a food intolerance?

Are you one of those people who is tired all the time AND who can't eat anything? No matter how "clean and healthy" your diet is, do you still get abdominal bloating, gas and pain?

Do you still struggle with skin rashes like eczema and hives even though you feel you have given up everything delicious in life? Do you sometimes just want to go mad with frustration?

Food intolerances are one of the most frustrating things to deal with when it comes to your health and time and time again I hear people wanting to just give up on their health because no matter how "healthily" they eat, they still react to everything.

If this is you, then I suggest that instead of giving up everything in one go, you try an Elimination Diet.

Food intolerances
Even healthy foods can cause food intolerances, but instead of giving up everything try to find out that one thing that you're intolerant to.

Unfortunately, an Elimination Diet is quite difficult to do correctly, but if you do it properly you may find you only have to give up one or two foods instead of everything you love - so it is worth doing properly!

Food Intolerance Vs. Food Allergy – What’s The Difference?

Before I get too far into this blog, I want to clarify the difference between food intolerances and food allergies because intolerances are very different to allergies and need to be treated differently.

A Food Allergy Is An IgE-Mediated Response

When you’re properly allergic to a food you will know within seconds to minutes of eating it because parts of you will itch and swell, you’ll probably struggle to swallow or breathe, and if you don’t get medical help soon there’s a good chance you could go into anaphylaxis (a severe, life-threatening condition).

When you have an allergic reaction to a food, your body has an exaggerated immune response to that food. This response is usually a Type 1 hypersensitivity reaction that involves immunoglobulin E (IgE). IgE is a type of antibody. Antibodies are proteins made by the immune system to help it recognise and fight foreign substances. When a person has an IgE-mediated response to a foreign substance, a number of different inflammatory molecules are released. You’ve probably heard of histamine – it is one of these inflammatory molecules.

Signs And Symptoms Of A Food Allergy

IgE-mediated responses occur rapidly, often within only a few seconds to minutes, and if you have an IgE reaction or food allergy, you’ll develop some of the following symptoms:

  • Itching or tingling in your mouth

  • Your throat, mouth, face, or other areas of your body may swell

  • Often it can become difficult to swallow

  • You can start itching, develop a rash, have itchy eyes and start sneezing

  • You may have difficulty breathing, feel dizzy or lightheaded

  • Sometimes you can become nauseous or start vomiting, have a sore stomach or develop diarrhoea.

It is vital that you seek medical help if you have an allergic response to a food.

Signs And Symptoms Of Food Intolerances

Food intolerances, on the other hand, are not IgE-mediated and do not cause such aggressive, fast-paced reactions. In fact, some symptoms to food intolerances only develop 48-72 hours after eating the food. This can make it quite difficult to find out what is causing the intolerance.

Here are some common signs and symptoms that can be related back to something you may be eating:

  • Abdominal pain or cramps

  • Bloating and gas

  • Diarrhoea and/or constipation

  • Irritable bowel syndrome (IBS)

  • Reflux

  • Headaches

  • Tiredness

  • Concentration problems

  • Foggy brain

  • Joint pain or muscular aches and pains

  • Snotty nose

  • Post nasal drip

  • Hives/urticaria

  • Skin rash, dermatitis/eczema

  • Mouth ulcers.

Food intolerances in children
Food intolerances are common in children and can often cause rashes, mouth ulcers or snotty noses.

How To Find Out Which Food Triggers Your Symptoms

The best way to find out what foods you’re intolerant to is to keep a food diary and take note of patterns of when you have any of the above symptoms, then give up these foods for a while and reintroduce them slowly to see if they are causing the problems.

This may sound easy but believe me when I say it is easier said than done! If you cheat even a little you will need to start again. That’s why I recommend you work together with a nutritionist or dietician who can support you. If you want to do it alone, then subscribe to my blog at the end of this page. Once you've subscribed you'll get access to my 'subscribers-only' page where you'll find all sorts of resources and guides including a downloadable step-by-step guide to doing an elimination diet.

How To Do An Elimination Diet

Step 1. Keep a Food Diary

Start by keeping a food diary for seven days. In it you need to record absolutely everything you eat and drink, as well as any possible food intolerance symptoms you may experience. Make sure you record the date and time of everything.

It’s important you are very specific when writing everything down. For example, don’t just say “pasta and bolognaise sauce for dinner”. Write down the type of pasta and all the ingredients in the sauce – all the vegetables, even all the spices!

Record any symptoms you experience during this time. Don’t only write down digestive symptoms such as bloating or pain. Also write down changes in your energy, your mood, your concentration levels. Even food cravings. All of these are important because they can all be linked to a food intolerance. Again, make sure you write down the dates and times you experience these symptoms.

After recording everything for seven days, go back through your notes and look for any patterns. It’s important here that every time you experience a symptom, you go through everything you’ve eaten and drunk up to 72 hours before experiencing that symptom. You will find that a few foods or drinks stand out as being constantly present within the 72 hours before your symptoms.

I call these the ‘suspects’ and hopefully you’ll only have a few. Now move onto Step 2.

Step 2. Eliminate The Main "Suspects"

This part can be really hard, especially because often it is the foods we crave that we’re intolerant to. Don’t ask me why, but time and again it’s the foods we really love, the ones we eat all the time that cause us problems. I see this often in little kids with dairy intolerances – they’re always the kids who love to drink glasses of milk or eat yoghurts or ice cream.

You need to totally, 100% eliminate any of the suspects on your list from your diet for at least two weeks. Hopefully by the end of those two weeks your symptoms would have gone. If they haven’t gone, then eliminate the foods for four weeks. Ideally, you should have at least five days of no symptoms before you begin step 3 which is called ‘the challenge’.

Step 3. Challenge One Food At A Time

It is a lengthy process isn’t it? Once you've had five symptom free days you can start challenging the suspects. It is vital that you only challenge one suspect at a time.

Start your food diary again and choose only one food to challenge. Eat that food for three days in a row. On the first day have only a small amount. Have a bit more on the second and have a good-sized helping on the third day.

Then wait two days to see if there are any symptoms. If there are any symptoms write down that food on a “TO AVOID” list and avoid it completely for at least three months.

If there are no symptoms at all please still avoid that food whilst you challenge the other foods.

Work your way through each food on your suspects list. Remember to do only one food at a time. Once you have finished challenging them all can you reintroduce the foods that caused no symptoms.

Be Careful When Challenging Foods...

I want to highlight something important here. When reintroducing foods, don’t reintroduce an entire food group at one time. You need to reintroduce, or challenge, each individual food one at a time.

For example, if you suspect you might have a dairy intolerance and you have eliminated all dairy for two weeks and are now wanting to challenge it, start with only one dairy product. For example, cheese. Once you know whether or not you can eat cheese, challenge another dairy product such as cream. Then yoghurt. Then milk and so on. People often find they can tolerate some dairy products but not others. You don’t want to stop eating all dairy when really you only need to give up cream, now do you?

If you do find you’re intolerant to a certain food, please find a good dietician or nutritionist to help you cut that food out of your diet. A mistake many people make when doing this alone is they cut out the problematic food without replacing it with an alternative. Over time this can lead to nutrient deficiencies and the myriad of health problems that comes with this.

Step 4. Reintroduce Foods

Once you know which foods you’re intolerant to, be sure to avoid them completely for at least three months (for some people it can be longer). Then slowly reintroduce that food over three days and take note of any symptoms you may develop over the next 72 hours. If you develop no symptoms, then you can start eating that food again. If you do develop symptoms, then continue to avoid it for another three to six months.


Doing an elimination diet is difficult and takes a lot of time and effort. However it is worth it. Just think – would you rather continue living with a bloated stomach, brain fog and mouth ulcers; give up all the foods you love just in case one of them is causing the symptoms; or do a few weeks of a hard elimination diet to discover the one or two foods that are really responsible?

Food intolerances often go hand-in-hand with an unhealthy gut microbiome. You can learn more about the gut microbiome in my blog A Quick Peek at Your Second Brain - The Gut Microbiome. I also have many other blogs on gut health and I've popped them all onto one page here >

I hope this blog helps you find out what foods are causing your symptoms. Don't forget to subscribe below and download your free step-by-step guide to doing an elimination diet.


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