MSDS: Material Safety Data Sheet
Looking in my workshop, nearly 100% of the "stuff in solution" there have solvents you do not want to breath. Then you do a bit of skiing and you see the composition of the waxes. You do a bit of woodworking and home improvement and you look at the composition of the glues. They are full of deadly compounds. So yes, we should not worry but still handle with care.
My simple advice: if you see on the product that it should be used in a well ventilated place, do it!
I use mostly safer compounds in my workshop (platinum-cure silicones, polyurethane resins, and occasionally good grade epoxy), but I still put on a proper mask, glasses, and gloves. Especially when working with my daughter. Those half-mask respirators are surprisingly comfortable (I found them easier to wear than N95/FFP2 masks).
AFAIK most allergies/hypersensitives are for harmless things; animals, pollen, and different types of food. So basing what we grow sensitive to might not be the best test to see if a product can cause harm
(For boatbuilding, the usual choice is polyester resin rather than epoxy, which is nasty in other ways. You don't wanna be inhaling those styrene vapors all day long.)
I got a kit with some fiberglass to fix a cracked bumper on a car. Don't want to do that ever again.
Epoxy is highly allergenic (or whatever the word is), so you should be pretty careful about using nitrile gloves or similar when working with it. Personally I don't find the smell particularly bad, and it's not very strong, at least compared to polyester resin.
Polyester, yes it smells bad, and as I mentioned in my parent comment that's styrene vapors you're inhaling, which is a known carcinogen. If I were to do some bigger job with polyester, I'd definitely want some pretty hefty breathing filter. But for the occasional one-off thing, particularly if you can do it outdoors, meh..