From the Guidelines
Histamine is a chemical compound naturally produced by the body that plays a crucial role in several physiological processes, including immune response and neurotransmission, and its release can cause various symptoms such as itching, sneezing, and inflammation.
Key Points About Histamine
- Histamine is primarily stored in mast cells and basophils and is released when these cells detect potentially harmful substances 1.
- When released, histamine causes blood vessels to dilate, increases blood vessel permeability, stimulates gastric acid secretion, and triggers inflammation, which can lead to uncomfortable symptoms like itching, sneezing, runny nose, and watery eyes during allergic reactions 1.
- Histamine also plays important roles in regulating sleep-wake cycles and appetite, which explains why some antihistamines cause drowsiness as a side effect 1.
- Antihistamine medications like diphenhydramine (Benadryl), loratadine (Claritin), or cetirizine (Zyrtec) work by blocking histamine receptors, thereby reducing these symptoms 1.
Clinical Relevance of Histamine
- Histamine is involved in the pathophysiology of various conditions, including allergic rhinitis, anaphylaxis, and atopic dermatitis 1.
- In anaphylaxis, histamine release can cause life-threatening symptoms, and epinephrine is the primary medical therapy for this condition 1.
- In allergic rhinitis, histamine plays a key role in nasal obstruction and other symptoms, and antihistamines can be used to alleviate these symptoms 1.
From the FDA Drug Label
Fexofenadine hydrochloride is a histamine H1-receptor antagonist The FDA drug label does not answer the question.
From the Research
Definition and Role of Histamine
- Histamine is a biogenic amine that plays a crucial role in both pro-inflammatory and immune regulatory processes, establishing itself as a key mediator in allergic diseases and immune responses 2.
- It is stored mainly in mast cells and basophils and is a prominent contributor to allergic disease 3.
- Histamine is capable of mediating various physiological processes, including neurotransmitter release, modulation of immune responses, and gastric acid secretion 2.
Histamine Receptors and Their Functions
- There are four receptor subtypes: histamine H1 receptor (H1R), histamine H2 receptor (H2R), histamine H3 receptor (H3R), and histamine H4 receptor (H4R) 2.
- These receptors are instrumental in mediating a variety of physiological processes, including:
- H1 receptor: mediating bronchospasm, edema, and mucus secretion in asthma, and pruritus, mucosal edema, and sneezing in allergic rhinitis 3.
- H2 receptor: mediating mucus secretion in asthma and allergic rhinitis, and gastric acid secretion 3, 2.
- H3 and H4 receptors: involved in regulating inflammatory responses and neuroinflammation in neurodegenerative diseases 4.
Histamine's Role in Allergic Diseases
- Histamine plays a primary role in allergic rhinitis, urticaria, anaphylaxis, and to a lesser degree, asthma 3.
- It is a key mediator in anaphylaxis, causing vascular permeability, smooth muscle contraction, and tachycardia 3, 5.
- Histamine-induced complications can affect various systems, including the gastrointestinal, cardiovascular, respiratory, and central nervous systems 2.
Therapeutic Interventions Targeting Histamine Receptors
- Antihistamines, including H1- and H2-antagonists, are critical for the treatment of symptoms and the inhibition of the progression of histamine-related conditions 2, 5.
- Mast cell stabilizers are also used to prevent the release of histamine and other mediators from mast cells 5.
- Newer antihistamines with decreased antimuscarinic and central nervous system side effects can be given in high doses, allowing more complete blockade of histamine receptors 5.