Describe how antihistamines work.

Histamine is a chemical messenger involved in a number of complex biological actions. It occurs mainly in an inactive bound form in most body tissues. When released, it interacts with specific histamine receptors on the cell surface. There are four types of histamine receptors  H₁, H₂, H₃, and H_4.

Antihistamines are usually synthetically manufactured drugs that inhibit the effects of histamine by binding to the receptors.

H1 Antihistamines inhibit the action of histamine by competitively binding to the receptors and therefore blocking histamine from binding to H1 receptors. (these are usually used to relieve allergic reactions like hay fever)

Histamine also has a role in the regulation of the secretion of acid in the stomach. H2 antihistamines are very effective in the regulation of the secretion of acid and the hormone gastrin. They are therefore great for treatment of peptic ulcers (a condition caused by excessive secretion of gastric acid) .

Each antihistamines target the same receptor as the histamine thus inhibiting the effects of it e.g allergies or ulcers

First, we have to understand how histamines work. Histamines work by inducing an increased level of vascular permeability, which leads to fluid moving from capillaries into the surrounding tissues. This further leads to increased swelling and vessel dilation. This effect can be stopped by antihistamines by antagonising the H-1 receptors and this translates into a clinical benefit, namely a reduction in allergy symptoms

During an allergic response white blood cells of the immune system, specifically mast cells, release a neurotransmitter called histamine. Histamine production in the body encourages inflammatory reactions to occur and this is what triggers the symptoms we experience during an allergic reaction or infection, such as itchy eyes, runny nose and sneezing.

Antihistamines are a group of medications that play a role as selective H-1 receptor antagonists. They work by blocking H-1 receptor sites; this leads to a blockage in histamine production. Additionally, the inflammatory response in the body is also then suppressed and this therefore allows us to control the symptoms we feel during an allergic response.

Anti-histamine work by inhibiting the effects of H1 receptors. They are a class of drugs commonly used to treat the symptoms of an allergic reaction such as swelling and itching etc.

Histamine is released in the body in response to harmful mediators, for example during an infection or an allergic response. It causes vasodilation and swelling. Antihistamines block histamine receptors and reduce swelling and are therefore taken to relieve symptoms of allergies, such as hay fever and reactions to bites or stings.

During the process of an allergic reaction, the body floods with histamine to try and combat against the irritant. However, the body often produces to much creating a cytokine storm. Anti-histamine combats against this issue.

Fellow Pharmacology grad here. Our body naturally produces a substance called histamine and is released from cells in response to something that can pose potential harm to the body, such as an allergic reaction, an infection or toxins. The signal for its release is an antibody known as immunoglobulin E (IgE). Histamine release results in expansion of our blood vessels and swelling of the skin at the problematic site. Antihistamines block the action of histamine by blocking H1 receptors, meaning histamine cannot take action. This prevents the harmful reaction from occuring, such as itching and swelling of the skin.

Hi Saul

Allergies are exaggerated responses to certain antigens called allergens. Take hay fever as an example – when pollen grains enter the respiratory system, they may attach to the antigen binding sites of specific antibodies.

This induces cells to release histamine which brings about the typical symptoms related to allergies, including sneezing, teary eyes and muscle contractions which can inhibit effective breathing. Antihistamines block receptors for histamine diminishing the allergy symptoms.

When something foreign or abnormal is detected in the body, a protein called histamines are produced as a response. Histamines cause blood vessels to expand and the skin to swell - giving you the symptoms of an allergic response.

Anti-histamines work by blocking the action of histamines, either by attaching to the histamine protein and changing its shape or by attaching to the receptors that histamine attach to resulting in the histamine protein becoming ineffective.