Histamine is a chemical your immune system releases. It’s mainly known for its role in causing allergy symptoms. But it has other important functions, like regulating your sleep-wake cycle and cognitive function. Antihistamines are a common medication that can manage histamine levels.
Histamine is a signaling chemical your immune system releases to send messages between different cells. Histamine has several functions, but it’s mainly known for its role in causing allergic and anaphylactic symptoms.
Allergies are your body’s reaction to a foreign protein. Usually, these proteins (allergens) are harmless. However, if you have an allergy to a particular protein, your immune system overreacts to its presence in your body.
A cascade of reactions leads to a release of histamine, which causes allergy symptoms. These symptoms are usually confined to one area of your body. If the immune reaction is severe, it causes anaphylaxis, which affects most of your body. Anaphylactic shock is life-threatening.
Your body mainly stores histamine in mast cells in tissues and basophils in blood. Mast cells are a type of white blood cell that are present in connective tissues throughout your body, especially:
Basophils are another type of white blood cell.
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Histamine regulates countless bodily functions and plays a key role in your body’s inflammatory response. The effect histamine has depends on which histamine receptors it binds to. Researchers have identified four types of histamine receptors.
You have H1 receptors throughout your body, including in neurons (brain cells), smooth muscle cells of your airways and blood vessels. Activation of the H1 receptors causes the well-known allergy and anaphylaxis symptoms. It causes:
Outside of allergic reactions, H1 receptors also help regulate:
You have H2 receptors mainly in the cells in your stomach that release acid, smooth muscle cells and heart cells.
Activation of the H2 receptors leads to:
H3 receptors are mainly involved in blood-brain barrier function. They’re found in neurons in your central nervous system. H3 receptors regulate the release of histamine and neurotransmitters like dopamine, norepinephrine and acetylcholine.
Researchers are currently studying H3 receptor antagonist medications for potential use in the treatment of neurodegenerative diseases.
H4 receptors are present in your bone marrow and hematopoietic cells (immature cells that can develop into all types of blood cells). They play a role in the formation of certain blood cells.
They also play important roles in inflammatory disorders and autoimmune diseases.
Histamine plays a central role in several allergic conditions, including:
Histamine intolerance occurs when you have a high level of histamine in your body. It can happen if your body can’t break down histamine properly. It causes a variety of symptoms, including:
Healthcare providers recommend or prescribe the following medications to help manage histamine levels in your body:
If you develop signs of seasonal allergies or an allergic reaction, reach out to your provider, especially if your symptoms are affecting your daily functioning. They can perform allergy testing and recommend treatments. Also, see your provider if you have symptoms of histamine intolerance.
A note from Cleveland Clinic
While histamine plays important roles in regulating normal bodily functions like your sleep-wake cycle and cognitive function, it can also wreak havoc when your body overreacts to otherwise harmless allergens. If allergies are affecting your daily life, see a healthcare provider. They can conduct tests to pinpoint your allergies and prescribe medications.
Last reviewed by a Cleveland Clinic medical professional on 03/28/2023.
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