My children's pediatrician used to tell me to pay close attention when I fed my young children (under two years of age) and to note if they didn't like the TASTE of certain foods. (Of course, vomiting would be even MORE alarming!)
At about 12 months, our son went from fussing, to welts, to excema and ultimately, to anaphylaxic shock. At that point, both children were tested for food allergies (I would imagine both YOUR children should be tested too!) and it turned out that the foods they had rejected as babies were the foods they were severly allergic to!
My boy was severely allergic to many things: peanuts, eggs, wheat, apples, etc. and his sister was allergic to quite a few DIFFERENT things! We changed their diets and eventually, they were able to integrate SOME things back into their diets (with doctor's supervision) but NEVER the biggies: peanuts or almonds.
Recently, my son had macadamia nuts which hadn't been on the original test. He vomited all night so we added it to his list of "don'ts". We still carry an epi-pen but both children have been brought up with "no fear, just caution".