Makes sense! I just wanted to know if I could introduce wood for them to chew on. I got the little bunny from someone who didn't wanna take care of it. Been caring for it since it was a week old so I was just curiousIt's not so much about allergies, but about how their digestion works. They need to grow the right bacteria to digest new stuff, so it needs to be introduced slowly to give them time for that.
Food changes with very young bunnies can be problematic, since weaning is already stress on their system, better stick to what it's used to. There is rather safe stuff, like plants of the rosea family (roses, brambles, apple leafs,...), narrowleaf plantain and others, a little oatmeal, that rarly cause any problem, but with a very young bun an upset stomach can be a fatal issue so, as said above, I would wait with introducing new stuff until they have enough resilience. The fallback safe food is hay.
So, it would be good for you to know what the dam is used to since the kit got it's set of gut bacteria from her.
For example, I raise my kits when fresh greens are plentiful, so that's the first thing they start to nibble after the nestbox hay, they get everything the does get, and that's quite diverse forage, some pellets and other stuff. I don't have to worry much about introducing stuff.
With 4 weeks, well, that's the earliest time to wean in an emergency, so be careful, don't rush things. I doubt they would chew wood much at that age anyway.
As bottom line: We can write a lot but can't really make relevant suggestions with the little information you gave.