My rabbit died 10 minutes after giving him a banana slice. It was the first time I gave him a piece of banana, he was 10 weeks old. Could this be an allergy or what? He started bleeding from the nose/mouth and yellow foam started to come out.

Wow that's really sad!

I can't seem to find too much information online about whether it's safe to feed rabbits bananas but the prevailing logic is that, because a rabbit's natural diet wouldn't include such exotic fruit, it's probably best avoided.

As for whether it was a banana allergy that proved fatal to your rabbit, I'm not sure. I'd have thought the sugar and starch content in bananas might have a detrimental effect, but one or two slices shouldn't be a problem... And a few users on other forums and Q&A sites seem to have fed their rabbits banana without such tragic results.

Perhaps your rabbit had an underlying condition that was triggered by eating banana.

Either way, I'm sorry for your loss.