What is histamine?

We know that hay fever symptoms can be frustrating, but it’s also really important to remember that hay fever and other allergic reactions vary in severity. Sometimes allergic reactions can require urgent hospital treatment, so you should never ignore severe symptoms.

Here, we’ll dive deeper into histamine, and just how it causes hay fever symptoms.

Histamine is a chemical that carries messages between cells. It’s made in the body by white blood cells called ‘mast cells’, but it’s also found in certain foods.²

Histamine acts as a signalling molecule, that plays an important role in many bodily functions such as:

Histamine is best known for its role in allergic reactions. When the body mistakes a harmless allergen, like pollen, for a potential threat it releases histamine.³

Histamine stimulates mucus production and opens the blood vessels so an army of white blood cells can rush to our defence. This leads to the classic symptoms of some common allergies such as puffy eyes, congestion, itching, and swelling.⁵

Histamine works to help stimulate stomach acid production.⁶  This then aids digestion and helps your intestines to move food, fluids, and waste.⁷

Ever wondered why you feel drowsy when you take an antihistamine? That’s because histamine has an important role in the sleep-wake cycle. It works to help promote wakefulness and keep you feeling alert.^8,9,10

Histamine is involved in various brain functions, like learning, your memory, and overall cognitive function.¹¹

Your body will naturally produce histamine, alongside enzymes which work to break down the histamine you consume through food.¹²

In some cases, you might not make enough of the enzymes needed to break down histamine. This may cause histamine to build up in the body, especially if you eat a high-histamine diet, leading to histamine intolerance.¹³

The histamines in food are produced by bacteria when food ferments or decays, so generally the fresher the food, the fewer histamines it contains.¹⁵

Fermented, smoked, cured, and preserved foods tend to be particularly high in histamines.

Other foods don’t contain much histamine themselves, but growing research shows that certain foods may stimulate, or ‘liberate’, the release of histamines from the body’s mast cells.¹⁶

Black, green and mate tea, energy drinks and alcohol may also contribute to histamine intolerance by blocking production of one of the enzymes involved.¹⁷

Some people find that following a low-histamine diet can help reduce allergy symptoms.¹⁶ While research into low-histamine diets is growing, the evidence available isn’t quite sufficient yet, and more needs to be learned when it comes to eating a diet low in histamine to manage histamine intolerance.¹⁶

A low-histamine diet includes eating foods such as:¹⁶ 

Low-histamine diets has gained a lot of interest from scientists with recent studies analysing an array of ingredients from eggs to wine, but evidence on which foods to avoid due to histamine levels or release in the body is still growing. Speak to a healthcare professional or a qualified nutritionist if you’d like to make a change to your diet to find out if it would be suitable for you.

 It’s thought that almost 41 million people in the UK have at least one allergy. Whether it’s hay fever, a food allergy or asthma, histamine is the reason why your body reacts the way it does. That’s why, when your allergy flares up, you might take an antihistamine to relieve your symptoms.

However, histamine does so much more than just trigger allergic reactions. This chemical works hard to support other bodily functions like regulating your sleep-wake cycle, aiding digestion, and helping you learn.