eli5 why holding a cold washcloth or a warm compress on your forehead helps a headache

Question

When I have a headache, I sometimes find a cold wet washcloth that I’ve put in the freezer for a bit will help, but sometimes it makes it worse, in which case, I use a heat pack I made out of rice and a sock, but when the heat doesn’t work, cold does. Why does one help sometimes but the other helps another time? I know heat helps with muscle pain and can help loosen the sinuses, but why does it vary? I also know using an ice pack on an injury helps because it reduces swelling, but why does a cold washcloth help a headache? I don’t think a headache is because your head is swelled. A bonus effect for me at least is that I also feel really relaxed after laying the cold cloth on my eyes, like it calms my mind. Any thoughts on that too?

In: Biology

Answer 1

I believe it has to do with the cold temperature constricting the blood vessels. If its a tension headache that might be why a heat pack works because warm temperatures relieves tension, like if you had sore muscles and needed to relax them.