Perhaps you relate in spring, as with red eyes, running nose and headache you suffer through the weeks of flowers and pollination. Perhaps your bus companion has decided to wear deodorant, good for one smell, but your poor immune system is out to get it! Or you’re out for the evening and you’ve been introduced to the wearer of particularly potent perfume … white blood cells launch full attack mode!
As your sinuses block you curse and (hopefully) grab an anti-histamine tablet and wait for the full effects to take hold.
But what do anti-histamines do?
As the name helpfully suggests, anti-histamines block the action of histamines. But that doesn’t help much. What is a histamine?
“histamine: a compound which is released by cells in response to injury and in allergic and inflammatory reactions, causing contraction of smooth muscle and dilation of capillaries.”
And the normal-person-speak translation is….
A histamine is a molecule in your body. It has a chemical formula C5H9N3, so 5 carbon atoms, 9 hydrogen atoms and 3 nitrogen atoms. It’s found in mainly in your body’s mast cells (at type of immune cell) and is released when your immune system detects a “nasty invader”. The histamines then trigger all sorts of reactions: swelling, inflammation, blood vessel dilation, sneezing, sniffles, itching.
Now these are great if say you’re cut and some bad bacteria get into your body. Then histamine causes the blood vessels to dilate (get bigger) so that other white blood cells can get out and engage in active combat or other cells go to help you to heal. Unfortunately, this dilation leads to swelling, fluid build-up, inflammation and more.
In an allergic reaction, the immune system waaaaayyy over-reacts to some stuff and causes the mast cells (with lots of histamine) to try and attach to the antigen (that’s the thing you’re allergic to). That’s all well and good. The mast cells are getting rid of the antigen, but there’s always a catch. As they do so, they release heaps of histamine into the area. And just like above, the histamines go around and cause all your horrible symptoms even up to anaphylactic reactions. Nasty, but remember that they’re also essential to fighting off the bad infections as well!
But how do we overcome this with anti-histamines? Well, the tiny little histamine can only work and cause these effects by binding to histamine receptors on cells. For example, if a histamine binds to a receptor on a mucus cell in your nose, that cell will start producing lots of mucus – a running nose. An anti-histamine binds to that receptor instead. So if you have all receptor sites taken up, then the histamines have nowhere to bind and CANNOT CAUSE A REACTION!
So next spring, or on the bus with your friend, this post will not help you at all. But as your eyes begin to sting and itch, you can remember how it all works. Not much of a comfort? Well at least you can say along with me, “damn histamine”.
But as per above, we do actually want histamine though 🙂