It sounds like a migraine.....when he first feels it coming on does he get tunnel vision or where he can only see half of things and has to look twice to see the whole item hes trying to focus on, give him four ibuprofen and let him lay down in a quiet dark room. The doc can prescribe things to prevent migraines and also to help make them go away when its already started. hope this helps.
To me, it sounds like your husband is suffering from migraines. I know how this feels because I suffer from them as well. For me, I lay down in a very dark room (people with migraines tend to be sensitive to light) with a cold wash cloth over my face. Aspirin and sleep are the best remedies for these headaches. As for what you can do, just be there for him. Try to help him rest.
Have him tested for food allergies. Or keep track of what he's eating and what he seems to be reacting to.
How long do the headaches usually last? Is it a pattern or 3 hours or 3 days or anything? These headaches could be migraines.
He needs to have pain medicine handy with him all the time. I found that Advil worked just fine as long as I took it within 30 minutes of onset of the pain. If you wait longer than that, the stomach stops processing forward and the nausea sets in and digestion wants to go backward (vomiting). Once forward progress stops, you can't process the oral pain medicine. Some people like Excedrin Migraine. For me, 3 Advil does the trick.