# Histamines, Friend/Foe?

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Ive just had a quick read about histamines in an old book, and from what I can tell they Dont seem to of much good to us.

1) they open up blood vessels when tissue is injured.

Surely thats the worst thing you want to happen, restricting them, and thus Blood flow would be far more beneficial I would have thought.

and 2) they also stimulate Hydrochloric acid production in the stomach when stressed.

now what evolutionary purpose can that possibly serve?

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you want more blood flow to an injured area because it more quickly and efficiently delivers the cells that will prevent infection and aid in healing, such as the formation of a scab (platelets).

stimulated HCl production probably leads to quicker digestion of whatever food is in your stomach, and to the absorption of the nutrients in that food. being stressed takes up energy. it's never a good state to be in.

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they cause hayfever. histamines are nasty and toturous

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histamine does not cause hay fever, an allergic reaction does.

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so what purpose do they serve in that mechanism then?

if taking ANTI-Histamines relieves it.

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histamine does not cause hay fever, an allergic reaction does.

I'm not sure if this is confirmed, but isn't the rise in hay fever due to cleaner living, where way back when, most people carried parasites and this balanced (for want of a better word) the immune system...take away the parasites and the immune system is over active, and attacks histamines. Somebody correct me if this is wrong though.

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I'm not sure if this is confirmed, but isn't the rise in hay fever due to cleaner living, where way back when, most people carried parasites and this balanced (for want of a better word) the immune system...take away the parasites and the immune system is over active, and attacks histamines. Somebody correct me if this is wrong though.

one of your body's responses to the allergen is to release histamines - it's an immune response. your body's immune responses are what cause a lot of the normal side effects of colds or injuries - swelling, for instance, is caused by and increase of blood to the area. a fever is caused by your hypothalamus raising your body's temperature after detecting the presence of a pathogen. You take anti-histamines so stop your body's flow of mucus, aka to clear up a stuffy nose, etc. histamines are not cells to be attacked, they're chemicals.

i think the whole "rise to cleaner living" thing does have some truth to it. after all, young kids who get out in the dirt and get sick and give their immune system excuses to build up, tend to not get sick as much as adults. I know I read a study somewhere about that, and anecdotally, my boyfriend is a living testament. As a kid he was always running around in the woods with his friends, and he got sick alot, but now he's healthy as a horse. Only been sick once in three years that I can remember. Allergies, I think, are from a substance that your body wasn't exposed to for a long time, and then was hit real hard once, and then every time after that it's exposed to the substance it has that same bad reaction. Again anecdotally, my boyfriend got stung by hundreds of bees once when he was a kid, and now he takes most insect bites pretty badly.

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Oops, I meant hitamines attack...i.e a defense mechanism, sorry rushed post.

Allergies, I think, are from a substance that your body wasn't exposed to for a long time, and then was hit real hard once, and then every time after that it's exposed to the substance it has that same bad reaction. Again anecdotally, my boyfriend got stung by hundreds of bees once when he was a kid, and now he takes most insect bites pretty badly.

Interesting, so an allergy (or in this instance hay fever) could be a combination of a rapid change in environment (increase in hygiene) i.e rapid relative to any evolutionary change, and a heavy exposure to a substance (in this case pollen) that promotes that same reaction, even at lower levels. I wonder if there's a correlation here...I know the farming of rape seed (in the UK anyway) has risen dramatically, just as an example. But, I'm probably jumping the gun a little here.

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They open up capillaries around a wound. Increased blood flow does nothing unless the thing with the bloodstream get get at the wound and any infection. This is why histamines are important, they let things like platelets and white blood cells out of the bloodstream and into the wound. Since this stops you a) bleeding to death and b) dying from ulcerous wounds, it's pretty useful.

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They open up capillaries around a wound. Increased blood flow does nothing unless the thing with the bloodstream get get at the wound and any infection. This is why histamines are important, they let things like platelets and white blood cells out of the bloodstream and into the wound. Since this stops you a) bleeding to death and b) dying from ulcerous wounds, it's pretty useful.

AKA Inflammatory response.

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AKA Inflammatory response.
Quite. It's as well to remember that not only is the inflammatory response a first line against infection, but healing in many cases is also an inflammatory process. Bone healing is a good example.

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so would taking things like caffeine and Ibuprofen help with hayfever at all?

as they work as anti-inflammatorys I believe.

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not as far as i know of. or at least i haven't seen any effect. but i haven't been looking for it. i'll do some experiments on myself over the summer.

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so would taking things like caffeine and Ibuprofen help with hayfever at all?

as they work as anti-inflammatorys I believe.

Probably not entirely, since not all of the symptoms of hayfever are due to the inflammatory response alone.

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The idea that, because antihistamines relieve (some of) the symptoms of hayfever, it follows that hayfever is caused by histamine doesn't quite wrok.

I woke up this morning with a headache and I took a couple of asprins. They made the headache go away. The headache was not caused by a shortage of asprin; it was due to too much whiskey last night.

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anti-histamines reduce all of the effects of hayfever. well, except the loathing of pollen.

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The idea that, because antihistamines relieve (some of) the symptoms of hayfever, it follows that hayfever is caused by histamine doesn't quite wrok.

I woke up this morning with a headache and I took a couple of asprins. They made the headache go away. The headache was not caused by a shortage of asprin; it was due to too much whiskey last night.

no one claimed this was the Case though?

the FACTs are the histamines cause an uncomfortable problem (regardless of the trigger), be it Whiskey that doesnt "Wrok" or pollen that sucks!

fact 2, Anti-histamines work, and relieve much of the uncomfortable feelings.

I don`t think anyone can argue these points.

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How do you interpret Insane alien's comment that "they cause hayfever. histamines are nasty and toturous" without thinking that someone claimed "hayfever is caused by histamine "? or do you accept that it may be a FACT that the claim was made?

Another reasonable hypothesis (albeit not really a FACT) is that if the histamine response didn't do more good than harm evolution would have dumped it long ago.

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i know pollen is the trigger. its just the histamines obviously play a major role in it as anti-histamines reduce the effects significantly. sorry for any confusion.

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Another reasonable hypothesis (albeit not really a FACT) is that if the histamine response didn't do more good than harm evolution would have dumped it long ago.

what, like the Appendix?

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so would taking things like caffeine and Ibuprofen help with hayfever at all?

as they work as anti-inflammatorys I believe.

No, they aren't...

Hayfever is caused by pollen causing degranulation of histamine from mast cells... Thus you prevent the symptoms of hayfever by blockade of histamine receptors... e.g. ceterizine blocks histamine H1 receptors...

Anti-inflammatory agents such as ibuprofen work by a completely different mechanism by inhibition of the enzyme COX... this would be a lot less effective with hayfever because it doesn't stop the allergic reaction...

In more severe forms of allergy, anti-inflammatory agents are used... but in such a case long-acting steroids are used.,.. these are a lot more effective anti-inflammatory agents than NSAIDs... just to make it clear, i'm talking about glucocorticoids - not anabolic steroids...

for example, in asthma people regularly take beclomethazone, which is an anti-inflammatory steroid to prevent inflammatation of the bronchioles... they also have salbutamol (b2 adrenoreceptor agonist) that causes bronchodilation if they have an asthma attack...

in very severe allergy... i'm talking about anaphylaxis (i.e. peanut allergy)... people are given adrenaline... also injectable anti-histamines and steroids can be given - e.g. diphenhydramine / hydrocortisol...

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Another reasonable hypothesis (albeit not really a FACT) is that if the histamine response didn't do more good than harm evolution would have dumped it long ago.

As was briefly discussed earlier, the large amount of allergies people suffer from these days may be a relatively new development, brought on by a change in lifestyle. It's still debatable, of course, but I'm inclined to believe it. In general the histamine response is good, it's your immune system at work. But we may have only recently created an environment for ourselves where it actually does more harm than good. Thusly, evolution hasn't had time to dump it yet. Especially since allergies like hay fever probably don't have a significant effect on fitness.

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