I am making standard DIY, cardboard and leather lens caps for my brass lenses. Aside from storing them in the open air as much as possible, are there any tips for keeping fungus out of my caps and lenses?

I don't think spraying/wiping my caps with leather fungicide sounds like a good idea given that I don't know a thing about outgassing with those products, but hopefully you kind folks have some experience and/or tips to share with me.

Alabama is reasonably humid, so moisture can be a problem where I am.

Thanks,
William