Stupid question about solids I'll probably get hate for

So my baby turned 6 months last week and we are starting BLW since he is showing all signs of readiness. Today I gave him one of those happy baby teethers that he LOVED. his face broke out a little bit but no where else. It wasn't a bad rash but it was on one side of his forehead.

Is it normal for babies to break out when starting solids? My grandma was saying that my mom broke out when she started eating real foods but after she had eaten certain foods for a couple of weeks, she stopped breaking out.

Her suggestion was that if the rash isn't bad, then to keep feeding him the foods and his body would get used to it?

I've never heard of this, but is it true? He never rashed bad. Just maybe 3-4 little spots on his forehead but no where else. It wasn't itchy and didn't bother him at all. Could it be his body being introduced to new foods?