Hi Gustavo - I am curious, are you asking this because you suffer headaches, or for someone you know (are you a teacher seeking help for a student?)
Before talking about yoga and headaches, please be aware that a headache may be a sign of something very serious and should be looked at immediately by a doctor, if you experience a headache with a fever, stiff neck, mental confusion, seizures, double vision, weakness, numbness or speaking difficulties, if you have a headache after any head trauma or injury. If you have any of these conditions, please get medical help as soon as possible.
So, lets assume your headache doesn't fall into one of the above categories: In general, before answering any health related question, it is very useful to know the cause of the problem before suggesting a prescription to cure it. Without knowing the cause, the cure could be worse than the original malady. So, do you know what is causing the headache? That is not a simple question because their are many kinds of headaches, but let’s assume you are referring to an ordinary run-of-the-mill tension headache, and not a migraine or a concussion.
Tension headaches, which everyone gets once in a while, are generally caused by tension, but exactly what is tense is not know. We don’t actually know the cause of tension headaches. We used to think it was from tight face, head or shoulder muscles, but recent research has shown this not to be the case, even though many treatments for tension headaches still suggest relaxing the muscles in these areas: that prescription can’t hurt, so you can try relaxing the head and shoulder muscles. Tension that is more psychological (i.e.: stress!) seems to be a more likely cause of tension headaches, so practices that can reduce our psychological stress seem helpful. This would include meditation, yoga and especially Yin Yoga!
Some yoga teachers suggest it is easiest to deal with a tension headache when it first starts: once it is underway, it is more difficult to stop the symptoms. I have not seen any medical studies verifying which yoga poses work best, but I will share with you some of the more traditionally offered postures, restricting myself to the ones we use in Yin Yoga, but just doing a quiet yoga practice with relaxed breathing and a good shavasana should help regardless of the postures being done (avoid stimulating postures like vinyasa movements and deep backbends.)
Easy forward folds: Caterpillar, Butterfly and Half-Butterfly — use supports like bolsters for the head and torso so that there is little muscular stress, Child’s Pose: maybe upon a bolster
Easy sitting or reclining twists
(I would not suggest Sphinx or Seal pose, but some people suggest Saddle)
You can combine any of these postures/practices with a few minutes of Ocean Breathing
: breathing in easily to a count of 4, pausing for 1 second, breathing out for a count of 4 and again pausing for 1 second. This will activate the parasympathetic nervous system and reduce the stress response. Another option often offered is to use an ACE bandage around the eyes. (Richard Rose describes how to do this in his Yoga Journal article
I hope this helps.