I've had a problem for several years thats getting worse and worse. When I change from artificial to natural light I get blinding headaches that last for hours and hours, and nothing I do can seem to take them away. Sometimes if it's really hot I get nauseous. I used to think it was dehydration - and it's quite possible the nausea is - but however much I drink I still get the headaches, especially coming out of work when I'm under artificial light for long periods. I wondered if anyone knows anything about this or has experienced something similar?