With the cup of ice, you don't hold it on one spot. Instead, you massage the area, with a towel handy to catch the dripping melt water. I and physical therapists have used it on my feet and legs, and hands and arms. With the ice moving and melting, I don't see how there'd be any danger. No matter how cold the ice is to start, it is 32 degrees when it melts.

I'm not sure I agree with always keeping a cloth between if you use ice packs for under 1/2 hour. Unlike the commercial cold packs or alcohol slush, if there's water in an ice pack, it is 32 degrees, not more or less, and can't get cold enough to cause damage. I've used a lot of ice packs over the years directly on my skin, and never had a problemproblemproblemproblem.