Solid food- resulting in hives? Or not?

Just started baby on solids. Following the “one new food for three days” rule to make sure he doesn’t have any reactions. We did squash for three days and I didn’t notice a reaction, but then we traveled so he didn’t have any solids for about a week. The last two days we have tried peas and within about 45 minutes he gets little red spots. I can’t tell if it’s his body just adjusting to solids, or if it’s an allergy to the peas? I don’t think it’s severe or a reason to go to the doctor because it doesn’t affect his breathing, no fever, he doesn’t scratch at them, and then fade within an hour or so. Just curious about personal experiences!