You might be more familiar with histamine as a cause of allergic symptoms like a runny nose, itchy eyes and itchy skin, but histamine can also be associated with IBS symptoms.

Can histamine cause digestive issues?

Histamine has three main actions in the digestive system

• affecting how fast the gut moves (gastric motility)
• production of stomach acid
• changing the amount of mucus in the intestines.

If you have high histamine levels your digestive symptoms could include abdominal cramps, diarrhoea, excessive gas and heartburn.

• Overproduction of histamine by mast cells in the gut may be responsible for diarrhoea.
• Stomach pains may be linked to histamine release in the colon

Other non-digestive signs of possible high histamine levels are congestion, itchy, watery eyes, headaches, anxiety, brain fog, and urticaria or eczema. It’s also been linked to symptoms of long Covid

Something I frequently see with histamine sensitive clients is insomnia, because histamine has an excitatory effect, meaning it’s hard to switch off.

Does SIBO increase histamine intolerance?

If you have an overgrowth of bacteria in the small intestine (SIBO) you may have higher levels of histamine for two reasons:

1. Increased histamine absorption due to lack of the enzymes to break down histamine. If you have SIBO you might make less of these enzymes, called DAO or HNMT. This is because excessive hydrogen or methane production by the bacteria can damage the lining of the small intestine.

The other reason for increased histamine absorption is that some bacteria actually create more histamine from food that we eat. Particular bacteria associated with higher histamine production are

• Hafnia alvia
• Klebsiella pneumonia
• Morganella morganii
• Citrobacter freundii
• E-coli

These may be found in people who have SIBO.

2. Increased histamine release – People with IBS may have an increased number of mast cells in the digestive tract. And they could be more active which would cause more digestive issues.

Mast cells contain histamine, and they can also activate and sensitize nerves in the gut. Mast cells may also modulate the integrity of the epithelial barrier (sometimes called leaky gut).

What is a low histamine diet?

It’s very hard to find an accurate source of histamine levels in our food, so it’s difficult to know how it will impact your IBS. However we do know that the things affecting histamine levels in your food include:

• the age of food (leftovers tend to have more histamine)
• length of fermentation process (the longer it’s fermented the more histamine)
• cooking method (frying and grilling increases histamine levels whereas boiling can reduce it in some cases. In this study the boiling of most meats (e.g. in a stew) decreased the histamine level.)

Some foods contain histamine, whereas some foods cause us to be less effective in getting rid of it.

• Some food contains histamine such as aged cheese, tinned meat & fish, deli meats.
• Histamines are higher in fermented foods such as yoghurt , wine or sauerkraut.
• Small amounts of naturally occurring histamine is found in tomatoes, spinach, aubergine and avocado. However, data on histamine levels is patchy and there is a real lack of evidence that shows vegetables are high in histamine. 
• Caffeine, chocolate, and alcohol metabolites can inhibit the activity of DAO, the enzyme which breaks down histamine, leaving you with higher levels.

Histamine liberators in an IBS diet

Some foods don’t contain histamine but it’s thought they may cause our bodies to release histamine. These include:

• Kiwi (often recommended for IBS- constipation)
• citrus (oranges, lemons, grapefruit),
• raspberries,
• alcohol

Can you eat eggs on a low histamine diet for IBS?

There is no evidence that eggs have high histamine levels or that cooking them changes the histamine levels. Some people may get a reaction to eggs, it could be due to the proteins in the egg white, or yolk, but it’s unlikely to be the histamine.

Does a low histamine diet help in irritable bowel syndrome?

If you haven’t yet already tried the low FODMAP diet, you might want to start there. The low FODMAP diet has been shown to lower histamine levels by up to 8 times. (I’ve got lots of blog articles about the FODMAP diet, the Beginners Guide to the low FODMAP diet is a good place to start.)

There is no harm in trying a low histamine diet for a few weeks to notice if your symptoms improve. Some people find their symptoms are worse when eating a higher histamine diet. You could also try taking an antihistamine to see if symptoms improve (with advice from your doctor).

This is quite a restrictive diet, and it’s important to get to the reason why histamine levels are high in the first place.

For example, do you have bacteria which are reducing your clearance enzymes (DAO) or creating more histamine from the food?

if you want to give this diet a try my suggested process for reducing histamines in your diet is

1. Remove high histamine foods for 2-3 weeks, as well as histamine liberating foods
2. If symptoms have improved move to phase 2 which is to bring back the histamine liberating foods one by one. If you get a reaction stop the trial, wait for the symptoms to clear before trying another food.
3. If this goes well you can trial higher histamine foods

If you want a recipe plan for eating a low histamine diet I have a 5 day meal plan to give you ideas for how to eat low histamine if you have IBS.