Antihistamines don’t prevent the body from producing histamine, but they stop histamine affecting your body’s cells in the usual way.
They do this by targeting special molecules called receptors, which are found in your cells.
Receptors
Receptors are protein molecules found in the cell walls. They react when they come into contact with certain other proteins.
To understand how receptors work, it’s useful to imagine a cell as a machine and the receptors as switches that are capable of changing how the machine works. However, the switches can only be used when the right key (the histamine protein) is used to activate the switch.
Antihistamines work by blocking the receptor sites in each cell in the same way that superglue can block a lock, so that the histamine ‘key’ can’t activate the receptors and affect the cell.
Histamine receptors
Four different histamine receptors are found in each cell. They are known as:
- H1
- H2
- H3
- H4
The H1 receptor is the receptor that causes inflammation. Therefore, the majority of antihistamines are designed to block the H1 receptor.
The H2 receptor is the receptor that helps to stimulate the production of stomach acids. Therefore, antihistamines that are used to treat stomach ulcers are designed to block the H2 receptor.
The H3 receptor seems to play an important role in stimulating the production of neurotransmitters, which are ‘messenger chemicals’ used by brain cells to transmit information around the brain. Neurotransmitters can have a powerful effect on your mood and emotional state.
The H4 receptor has only recently been discovered and not much is known about its role, although it’s thought to be involved with the regulation of the immune system.
At present, there are no commercially available antihistamines that can block the H3 or H4 receptors. However, current research is underway to produce such an antihistamine.
It’s thought that H3 blocking antihistamines could be useful in treating mental health conditions, such as depression, as well as neurological conditions, such as Alzheimer’s disease. Recent research also suggests that H3 blocking antihistamines could be useful in helping to relieve neuropathic pain (pain caused by damage or irritation to the nerves).
It’s thought that an H4-blocking antihistamine may be useful in treating autoimmune conditions, such as rheumatoid arthritis, where the immune system attacks healthy tissue.
Blood:Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Blood vessels:Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.
Brain:The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
Drowsiness:Drowsiness is when someone feels extremely tired and uncontrollably near to sleep.
Fever:A high temperature, also known as a fever, is when someone’s body temperature goes above the normal 37°C (98.6°F).
Sneezing:Sneezing is an involuntary expulsion of air and bacteria from the nose and mouth.
Stomach:The sac-like organ of the digestive system. It helps digest food by churning it and mixing it with acids to break it down into smaller pieces.
Tissues:Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.
Ulcers:An ulcer is a sore break in the skin, or on the inside lining of the body.
Vomit:Vomiting is when you bring up the contents of your stomach through your mouth
Google+
How antihistamines work
