Caffeine can cause vasoconstriction by blocking adenosine, potentially relieving headaches associated with vasodilation.

“drinking a cup of coffee or getting caffeine through tea is a great way to deal with headache why would that be well it turns out that coffee can cause either vasoconstriction or vasodilation depending on when you take it and we'll get into the use of caffeine as a treatment for headache because indeed it can be a very potent treatment for headache but you absolutely need to know what kind of headache you are experiencing because in some cases drinking caffeine whether it's in tea or coffee can absolutely alleviate the pain of a headache especially if you catch that onset of a migraine or attention type headache early on”