I spilled some DEET on a desk as a kid, and it stripped the varnish clean to the wood. Great if you want to take that long-procrastinated woodworking project camping?
Almost as effective. But in a trade off picaridin is better vs flies and gnats. I feel a few percent less effective vs mosquitoes is worth what I hope is a less toxic repellent. It was first developed in the 1980s and is derived from peppers.