I'd be more worried about ear-sweat and other build-up. Your ears need ventilation or they can get infections or other bad stuff. I know whenever I use earplugs I get a lot of wax build-up. Neil Peart had an ear infection because of too much use of in-ear monitors and motor-bike ear plugs.
That said if you can't get to sleep any other way it might be worth the risk.
That said if you can't get to sleep any other way it might be worth the risk.