No advice hun but big that would have been scary!
A friend of mine had a little boy who was allergic to something in milk (I think it may have been milk protein? Can't remember 100%) and every time she had any form of it (even if it wasnt specifically dairy, but something that contained the allergen) he would break out in HUGE rashes and be a very sick little boy he didnt have the anaphylaxis but it was a very serious reactiob nonetheless.
Basically, she saw allergists and paedatricians and they all said that unless she wanted to wean, she had to cut the allergen completely out of her diet. Which was very hard, but a decision she wanted to make.
If he didnt have that allergen in his (or her) diet, he was fine, no reactions or anything and was happy, and they continued to have a successful bfing relationship.

Hope that was of some help x