Doesn't mean it doesn't happen...and just when was the last time your snakes TOLD you what they're feeling?
FYI- aspen is fairly soft wood fibers, but it's possible that all brands are not of the same quality, or that they contain contaminants. A similar & KNOWN situation happens with sand...it was found that sand has nearly-microscopic sharp edges that can cut into the snake's skin (between & UNDER their scales) causing infections. While sand is a common component outside, very few snakes evolved to live exclusively ON it, and I'm pretty sure BPs did not evolve living on aspen either. OK?