Well, it depends on the baby. I have 4 kids. My first had no issues. My second could not tolerate dairy as a baby. He is 3 now and I just cut dairy and gluten out of his diet because of eczema. His eczema goes away when he is off gluten. My 3rd child could not tolerate dairy or soy as a baby. Dairy gave him bloody/mucus poop and soy made him vomit. My daughter is 8 months old and is on a hypoallergenic formula. She is very sensitive to stuff. Dairy made her vomit and made her have blood in her poop. I have not introduced her to any gluten/wheat and never will. She also will not get cows milk when she turns 1. My daughter has eczema and I'm still trying to figure out what is causing it. She also has an allergy to berries. I have pushed my way of eating on my kids, so they eat very healthy now.
Every so often my kid (16 months old) will get in to some other kid's wheat junk when we're visiting friends. He has no reaction, physical or behaviorally. Then again, his gut isn't populated with a bunch of candida garbage. He's been exclusively breastfed for 16 months and his first solids were lamb, egg yolks, and liver. He's still a little leaky... seems to react with a little rash to egg whites, night shades, and non-fermented/raw dairy but amazingly enough there was no reaction to wheat or other grains that he's occasionally got his grubby little fingers on.
Different babies, different strokes? My boyfriend went into anaphylactic shock the first time his mom fed him solid food, so that must have been exciting (he was allergic to EVERYthing). Zero interesting things happened to me when my mom started giving us bones to chew on or mashed potato. My brother got mad rashes when fed tomatoes or wheat. My older brother got really congested when he was fed dairy. Some kids react to things, some don't. I never had a rash or eczema or colic, and I was fed everything my brothers were, but they experienced all three of those things when they were really little even after my mom cut out gluten (tomatoes, berries, and dairy seemed to be the real culprits).
It really depends on the child. I've been in early childcare centers and some children have serious allergies...others eat everything in sight, minus spoon. If you're thinking the "majority" I think most react quite fine to dairy and wheat since the center menus focus on that. But then again, the children are non-verbal so you don't know how they're feeling.
But wearing the food on their head and making the biggest mess possible seems to be a common denominator.
My daughter had her first bite of wheat with her 1 yr cupcake. I was terrified, but no issues whatsoever. Since then she has had her fair share of goldfish and almond butter/jelly sandwiches. I'm guessing she inherited my high tolerance to any and everything bad for you. But it's different for the individual. Babies, after all, are just younger humans. ;)
My first baby (breastfed), reacted with lots of gas and a couple of sleepless nights after we introduced rice meal into her diet. We stopped right away. I stayed with sweet potato, avocado, etc after that. One night I BBQd salmon, and she was like a ravenous animal (9 mo.). It was so much fun to watch her devouring that fish. Second baby we just started on avocado and berries. No reaction at all.
In the UK we tend not to let babies have cow's milk until a year old. Many of us breastfeed for a year or more so that baby will be getting breast milk not cow's milk although its mother might drink milk of course. Secondly solids are only really needed from 6 months - fat babies might be fed solid food far too early but there is no rush at all.
Some parents use prepared baby foods and others just whole foods.
None of my children have food allergies and most of tehm probably picked up and ate a bread roll in their hands when they were 9 months old or something like that.