Can IBS be made worse by allergies?

Nutritional Practitioner, BA (Hons), DN, DNT (Distinction)
Ask Ali

15 July 2019

What causes allergies?

First of all, let’s talk allergies. Most of us will have experienced an allergic reaction before: itching, swelling, nasal congestion and watery eyes are just some of the symptoms that you may be familiar with. Whether a particular food has prompted a reaction or you are sensitive to certain pollens in your area, an allergic reaction can be uncomfortable and interfere with your day-to-day life.

An allergic reaction occurs when your body’s natural defence system over-reacts to a harmless substance such as pollen, animal dander or dust. Certain foods can also trigger a reaction, particularly if your digestive system isn’t doing a great job. If your immune system mistakes one of these substances in a food product for a harmful pathogen, it will release histamine as part of its defensive reaction.

Despite its negative connotations, histamine is actually very useful. It is stored in various places in the body including the sinuses, lungs and gastrointestinal (GI) tract, stimulating stomach acid production and widening blood vessels to allow white blood cells to reach the site of injury. However, it is when too much histamine circulates around the body that problems can arise.

How are allergies linked to IBS?

Poor digestion and allergies have a complex relationship. Research has suggested that people who suffer from allergic rhinitis are more likely to have IBS,1 while similar research has shown that foods containing histamine can trigger IBS symptoms.2 So, why is this the case?

As mentioned above, histamine is involved in the dilation of blood vessels, which can cause dizziness. Since histamine is an inflammatory chemical, too much can also lead to itching, swelling and irritation of the skin. It is also involved in the contraction of respiratory airways so, when too much histamine builds up in the body, this can cause allergy symptoms such as a runny nose, wheezing and watery eyes.

However, a build-up of histamine can also result in symptoms which are less associated with allergies and more commonly identified as complications of IBS. This is related to histamine's role in the secretion of gastric acids in the gut and can cause diarrhoea, stomach pain and nausea.

Can IBS be made worse by allergies?

From this we can see that allergies can in fact contribute to IBS symptoms as the histamine which is released during an allergic reaction can produce gastrointestinal symptoms as well as the well-known runny nose and itchy eyes.

Can allergies be made worse by IBS?

On the other hand, it is also possible for poor digestion to affect allergies: this can increase how much histamine is circulating in the body which, as we know, can trigger symptoms such as congestion, itchiness and watery eyes.

The reason behind this is that, if you have poor digestion, it can reduce the activity of diamine oxidase (DAO) which is responsible for breaking down histamine that comes from foods. In addition, excess histamine from food sources will permeate the gut wall into your bloodstream. As a result, you could suffer from allergy symptoms without being exposed to specific allergens.

How can I avoid making IBS and allergies worse?

It is clear that a complicated relationship exists between allergies and IBS, with a vicious cycle of poor digestion contributing to excess histamine floating around in your bloodstream and high histamine levels causing symptoms of IBS. So, how can you avoid a build-up of histamine which could mimic an allergic reaction and potentially cause or worsen your IBS symptoms?

1. Avoid high histamine foods

As I’ve mentioned, certain foods contain significant levels of histamine and can increase your risk of histamine build-up. It is best to avoid foods which are high in histamine, such as:

  • Alcohol
  • Caffeine
  • Processed ready meals
  • Fermented foods
  • Refined sugars.

You can read this blog from our Allergy advisor, Louise, to find out more about foods which could be contributing to your allergy symptoms.

2. Be wary of histamine liberators

Some foods do not contain histamine themselves, but promote the release of histamine from other foods. These include citrus fruits, nuts, beans, pulses and fish. Rather than cutting these out altogether, opt to cook nuts and beans rather than eating them raw. Also, make sure to eat fish which is very fresh or has been frozen while still fresh – foods which have fermented and over-ripened can cause issues.

3. Sit up straight and eat slowly

Taking care while eating can improve your digestive function too, so:

  • Make sure you sit up straight to allow plenty of room for your digestive processes to take place
  • Take your time while eating - bolting your food causes bloating and excess gas. Make time at work to stop and eat lunch to give your body a chance to relax, as stress can slow down the digestive process
  • Chew your food thoroughly. This is the first step of the digestive process and is a very important one as it activates the production of digestive enzymes and primes your stomach to release food.

4. Look at FODMAPs

A low-FODMAP diet has been found to reduce histamine levels in the body. One study asked 20 IBS sufferers to consume a low-FODMAP diet and 20 IBS sufferers to consume a high-FODMAP diet to determine if this would improve their symptoms.

In the low-FODMAP group, histamine levels were reduced eightfold and IBS symptoms significantly improved.3 It could be worth looking into reducing or eliminating FODMAPs from your diet to reduce your IBS and/or allergy symptoms.

Find out more about FODMAPs and IBS.

5. Try probiotics

Probiotics can be used to improve levels of friendly bacteria within the gut which can help to strengthen the gut wall and improve digestion. They may also support the immune system by introducing a variety of bacteria into the gut – many people nowadays are ‘too clean’ and are not exposed to a wide range of germs which, in turn, could mean they are more sensitive to harmless allergens.4

Optibac Everyday contains 6 different strains of good bacteria which have been shown to reduce inflammation and ease respiratory symptoms associated with histamine production.5 Our friends over at Jan de Vries supply Optibac Everyday probiotics or, alternatively, you can find these in your local health food store.


My Top Tip:

Molkosan is a prebiotic which is rich in L+ lactic acid. This can be taken alongside probiotics to provide a healthy gut environment in which good bacteria can thrive, and increase the likelihood that probiotic supplements will work well.

"Works a treat, tastes lovely. Fantastic quality, perfection."


Read what other people are saying about Molkosan.

6. Tackle stress

As I mentioned briefly above, stress can affect your digestion by reducing blood flow to the digestive organs. This can slow down digestion and have nasty effects on the body, such as constipation and bloating.

What’s more, stress can also increase the production of histamine and this is the last thing you want if you are suffering from a messy combination of allergies and IBS symptoms.

In order to tackle stress, talk to a friend or counsellor about any personal issues that are troubling you. You may be surprised at how much it can help to talk about your feelings out loud. Alongside this, you can try Stress Relief Daytime, a gentle blend of valerian and hops which can soothe mild stress and anxiety.



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Did you know?

How you eat rather than what you eat can also trigger your IBS. From not chewing your food enough to even how you sit while you eat can all impact affect your IBS!

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