[city41]

This site says just the opposite

> Caffeine narrows the blood vessels in your brain. Without it, your blood vessels widen.

https://www.healthline.com/health/headache/caffeine-withdraw...

[bryanlarsen]

Okay, I may have the mechanism wrong, but you've confirmed that it's active in brain blood flow. It's definitely an effective medicine and complement, at least for me. It's included in many OTC cold & headache mixes for a reason.

[city41]

Yeah, for sure. This post and these comments just made me google caffeine for a bit.

If I don't get my morning cup I almost always get quite the headache, so I'm not surprised.