Really sounds to me like a circulation thing.
The no exercise, and I'll guess that he may not drink any water, could be part of it.
Coupled with bad diet. Probably on the road its fast food with plenty of white flower products.
Somethings going on thats making the lymph system work overtime.
My best suggestion is to cancel the doctors appointment. It will save you money and prevent a condition being worsened by drugs.
Have him drink lots of water. This will give the blood system the fluids it needs get moving.
Give him a bag full of fruits to chew on before he leaves on a trip.
This will give him something healthy and easy to digest that has nutrition in it and he won't have so much room for fast food.
He could eat salads. They're usually available everywhere.
This kind of improved diet and added water will make it easier for the lymph system to do its job and give it less work.
Also he should really avoid any coffee or sodas, these close up blood vessels, restricting flow.
And I would suggest having him throw a little cayenne powder in juice and drink it from time to time. This will help greatly with the blood system, it will open up the vessels and energize him.
And last, ask him to force himself to get in some exercise. Even if its just walking around a truck stop.
He'll feel better by it too.