Why do things seem so loud and/or so bright?

Sensitization. Some of the processes translated in nervous tissue has multiple step processing like sounds tranferred to words--this require mechanical to electrical then chemical changes---in migraine light get bright because first messanger which is tolerable trigger a second messanger which is different than usual and may be painful--called allodynia--like I have headache and my hair hurt when i touch it.
Migraine. If this is episodic. You may be suffering from migraines or complex migraines. You don't necessarily have to have a headache to have a migraine.