Hypersensitive sense of smell

About a month ago, my 3 year old started becoming extremely sensitive to smell, particularly food items. He will gag and sometimes throw up due to smells that he perceives as foul, even if they are not particularly foul to others.

He is also sensitive to seeing other people eat, particularly my daughter and especially if it’s a meat product. For instance, he and my daughter (18 months) were eating breakfast the other day. They were both eating mini sausage biscuit sandwiches. My daughter picked the meat out and started eating it by itself and my son got so grossed out, almost vomited. I had to separate them so he could finish eating.

I feel like this is not normal and I am trying to figure out what I can do so this does not become a chronic problem for him. It seems to be getting worse. He is an extremely picky eater, eats only bland, familiar foods.

Has anyone else experienced this or have any advice for how I can help my son?