Hello and hope you are doing well.
Allergic reactions are mediated by IgE antibodies, which are released on exposure to a particular allergen. These in turn activate mast cells and lead to a local response or systemic anaphylaxis. So, antihistamines might help, but sometimes the allergic reaction depends on the quantity also. So it's best to avoid those foods.
Also, long-term use of the antihistamines could cause mild & transient side effects such as headache, dizziness, drowsiness, agitation, dry mouth and GI discomfort.
Hope this helped and do keep us posted.
Potentially, but eating a food you know you are allergic to is a recipe for disaster. Allergies can change and worsen at any time, just like they can appear or disappear without warning. You are best to avoid or find a substitute.