Understanding One of the Body’s Most Important Chemical Messengers
When most people hear the word histamine, they immediately think of hay fever.
In reality, histamine is far more than an allergy chemical.
It is a naturally occurring molecule produced by your body that plays an important role in many normal functions, including:
- Immune defence.
- Healing after injury.
- Stomach acid production for digestion.
- Communication between nerve cells.
- Regulation of blood flow.
Histamine is essential for life.
Problems arise when too much histamine is released, when it is not broken down efficiently, or when mast cells become overactive.
What Are Mast Cells?
Mast cells are specialised immune cells found throughout the body, particularly in areas that come into contact with the outside world, including:
- The skin.
- The respiratory tract.
- The digestive system.
- Around blood vessels and nerves.
They act like early warning sentinels, constantly monitoring for potential threats such as infections, parasites or allergens.
When activated, mast cells release a variety of chemical messengers, including:
- Histamine.
- Tryptase.
- Prostaglandins.
- Leukotrienes.
- Cytokines.
These substances help coordinate the body’s immune response.
Histamine – Friend and Foe
Histamine is not harmful.
In fact, without it our immune system could not function normally.
During an allergic reaction, however, histamine can produce familiar symptoms such as:
- Sneezing.
- Itchy eyes.
- Runny nose.
- Skin flushing.
- Hives (urticaria).
- Swelling.
- Itching.
These responses are part of the body’s defence system, although in allergy they occur in response to substances that are usually harmless, such as pollen.
Histamine Sensitivity
Some people report symptoms that they believe are triggered by foods naturally high in histamine or by reduced ability to break histamine down.
This is often referred to as histamine intolerance or histamine sensitivity.
Research into histamine intolerance is ongoing. Although some people report improvement with dietary changes, there is currently no universally accepted diagnostic test, and symptoms can overlap with many other conditions.
Symptoms sometimes attributed to histamine sensitivity include:
- Flushing.
- Headaches.
- Nasal congestion.
- Digestive discomfort.
- Itching.
- Hives.
- Palpitations.
If symptoms are persistent or troublesome, assessment by a healthcare professional is important to identify the underlying cause.
Mast Cell Activation Syndrome (MCAS)
Mast cell activation syndrome is a recognised medical condition in which mast cells release excessive amounts of chemical mediators inappropriately or too readily.
Unlike seasonal allergies, MCAS may affect several body systems at the same time.
Possible symptoms include:
- Recurrent flushing.
- Itching or hives.
- Abdominal pain.
- Diarrhoea.
- Light-headedness.
- Wheezing.
- Low blood pressure.
- Episodes resembling allergic reactions.
Diagnosis requires careful medical assessment and should only be made by clinicians experienced in mast cell disorders.
Histamine & the Skin
Histamine plays an important role in many skin conditions.
It contributes to:
- Itching.
- Redness.
- Swelling.
- Increased blood flow.
However, not every itchy or inflamed skin condition is caused by histamine alone.
Eczema, psoriasis, rosacea and acne involve multiple inflammatory pathways, which is why treatments vary depending on the diagnosis.
Looking After Your Skin During Allergy Season
If you experience seasonal allergies:
- Wash pollen from your face and hair after being outdoors.
- Use a gentle, fragrance-free cleanser.
- Keep your skin barrier healthy with an appropriate moisturiser.
- Wear broad-spectrum sunscreen every day.
- Consider sunglasses outdoors to reduce pollen exposure to the eyes.
- Follow the advice of your GP or pharmacist regarding allergy treatment.
A healthy skin barrier may also reduce irritation from environmental factors.
Can Diet Help?
A varied diet rich in colourful fruit, vegetables, whole grains, legumes, healthy fats and oily fish supports overall health and provides nutrients that contribute to normal immune function.
Some people with suspected histamine intolerance explore a low-histamine diet under professional supervision, but this should not be started without guidance. Many histamine-rich foods, such as tomatoes, spinach and fermented foods, are otherwise nutritious, and unnecessarily restricting them can make it harder to achieve a balanced diet.
Supplements such as quercetin are being researched for their potential effects on inflammatory pathways and mast cell activity, but current evidence is not strong enough to recommend them routinely for histamine intolerance or MCAS.
