Son allergic to bananas?

My son is 5 and half months, hes been getting cereal since about 4 months and has tried beans and peas with no problems. I tried pureed bananas(baby food not an actual banana) and within minutes he had big red blotches all over his head and face. I stopped immediately and they went away. Im just wondering if anyone else went through this, and if you could eventually feed them bananas or if its a permanent allergy? P.s I will ask my doctor tommorow, but im just curious.