Allergic reaction to veggies?

I've read articles from numerous sources that recommend alternating protein sources to avoid food allergies. Would the same concept apply to vegetables? I can't seem to get enough broccoli and kale and would hate to have to give those up....

if you have hay fever there can be cross reactions with some veggies like carrots and apples. also, things like celery and some winter veggies are highly allergic for some.

with brocoli there are other concerns like goitrogens that could suppress thyroid function if consumed too much.

as the saying goes, one mans medicine is another mans poison (or something like that )