#2 Paper Towels
Since we spoke about dampness already, you can imagine why it is a bad idea to keep your paper towels in the cupboard under the sink. It is a given that you may end up having some sort of dampness in there from all the plumbing, so holding your paper products under there is not a good idea.
And while we are focusing on paper towels, this is a rule that you should follow no matter if it is them or if we are talking about other paper products. This also includes toilet paper or things stored in paper bags. Paper products are made to biodegrade quickly, which makes them very fragile when they come in contact with water or moisture. So do yourself a favor and do not store them there.