Scientifically and biologically, how does caffeine alleviate certain kinds of headaches?

Caffine opens blood vessels, allowing more blood flow.

@filmfann what exactly does that mean in the scheme of alleviating the headache?

If your body is addicted to caffeine and you go without caffeine for awhile, caffeine will get rid of your headache. I’m not being a smart ass. There could be another reason, as well.

I rarely drink caffeine. I avoid it unless I have a headache. I’m pretty sure that’s not it.

Headaches are often caused by the constriction of blood vessels so @filmfann says, the caffeine acts a a vasodilator and helps alleviate the headache. I don’t use caffeine regularly either but I know my prescription migraine pills have caffeine in them along with the other stuff.

Pretend I know nothing about the constriction of blood vessels. Why does that cause a headache?

The section here on Primary Headaches and their causes has some discussion on blood vessel involvement.

Is Biology not Science?

Small amounts of caffeine helps increase the absorption of the medications in headache remedies. However, if you normally drink a lot of caffeine (Mountain Dew, Red Bull, Cokes, coffee, tea, etc.) then quitting cold turkey will cause headaches until your body withdraws from the caffeine. It enables you to take lower doses for relief. It seems to work better on tension headaches, not migraines.

For the physiology of a headache, see headaches

Vasodialator. See a more technical explanation here http://en.wikipedia.org/wiki/Caffeine skip down to Effects When Eaken in Moderation and Tolerance and Withdrawal.

I think caffeine works best really on caffeine withdrawal headaches, not on all headaches. I think most people don’t realize how addicted they are, and when they skip their caffeine hit, the headache is going to kick in. I always say, if you drink it regularly make sure you drink it. If you don’t better to not start.

@filmfann , @janbb , and @JLeslie seem to have it backward. Caffeine is a vasoconstrictor—it causes vessels to narrow and thereby reduces blood flow. Increased blood flow is thought to be associated with the onset of headaches, especially migraines. Caffeine also speeds the absorption of other painkillers from the stomach, as pointed out by @PandorBoxx. Specific molecular mechanisms are described in the Wikipedia article on caffeine.

It’s well known that the brain itself is insensitive to pain. The brain coverings (meninges) and other connective tissues in and around the brain, scalp, and neck are where the pain actually is generated. Increased blood flow can irritate or stretch these tissues, causing headache.

That might be right actually, vasoconstrictor, either way it is the withdrawal, not the consumption of the caffeine that gives you the headache. And, so caffeine can remedy it. But, be warned that it takes a while to feel better. If you have a headache advil will help in about 45 minutes, the caffeine takes longer.

I’ve never once had a noticeable caffeine withdrawal headache (e.g. in the morning). Average intake is on the order of ~4×20oz cups of coffee a day during the work week. But I can get a severe headache when I’ve had too much caffeine. Say like 6pm when I’ve had 8+ cups.

Or… is that actually the point where you start to have withdrawal – right as you’re coming down from 8 cups? But at that point drinking more only increases the headache.

This whole topic has always baffled me, because I seem to be reversed somehow.

I really meant for non-withdrawl cases to be the ones considered…

That’s what Ithought you meant.

@ipso My experience is that is takes 14–24 hours to start getting the headache. For my husband and I, if we don’t drink caffeine during the day (back when I drank it, he still does) the headache came on between 1:00 and 3:00 in the afternoon. Even if he had a soda for lunch, it would not quite catch it in time to miss the headache completely. I never drank as much as you though, so maybe your would come on faster?