Yeah, we kind of need to know what kind of job it is because something particular can be causing it. he could even be allergic to something he's working around. Another thing that is overlooked a lot because its not serious are panic attacks. Panic attacks will happen sometimes at curtain times or places because its brought on by stress, fear, and worrying. Symptoms for a panic attacks are dizziness, nausea, racing heartbeat, sometimes skin will go numb or tingle, sweating, chest pain, hot or cold flashes, choking feeling, and shaking. If he is nervous at work then he can very well be having panic attacks which will be overlooked. Sometimes a person will have them out of the blue even when theyre not nervous. I started having mine from stress then it turned into a disorder. A psychiatrist will know so if no luck with anything else then he may need an anti anxiety medication(adavan/clonazepam) works better than anti depressants they try to give. hope this helps
if his workplace has dust chemicals it could be linked to a respitory issue.is it a temp.controlled area? is it in the morning mostly? it my be a simple fix like eating a good breakfest.the reason they removed his gallbladder is thats the symptoms for a gallbladder problem.did this start when he first started the job? does he have a weight issue? if he has to bend over alot it may be reflux. if symtoms persist you may have to change doctors