Headache Causes More Condition_symptoms What Causes Severe Headache And Subsequent Nausea?

What causes severe headache and subsequent nausea? - headache causes more condition_symptoms

I'm more interested in the medical aspect of what's really happening in my body to create this pain. Why are nausea and vomiting in the picture?

He suffered a terrible headache yesterday, which I suspect the origin of dehydration after a gym class, but still much water to drink later, the headache got worse and I began I feel sick. The puzzle is worse after a few hours. If dehydration is the reason why the drinking water?

Thanks for serious answers.