The allergy part may sound outlandish but it happened to me with headphones. They were made of some kind of rubbery plastic which was absolutely fine for the first 2 years I used them, and then they became impossible to wear. Cleaning the headphones did nothing and the allergy got pretty gross, I had to see a doctor. Fortunately an ointment fixed my ears but I had to get new headphones. My guess is that the material they were made of started to degrade/change chemically with time, like faux leather and rubber does, and my skin developed an allergy to it.