Remember kids... always wear a helmet. (The almighty bikeradar helmet thread)

It's true,
I've seen the damage they can do i really think it is a good glue bad glue thing. Also what the shell is made from.

Years ago I remember being told that stickers damage helmets. Some chemical reaction. Now it sound rubbish to me as most helmets come with at least some brand name sticker on them. However my knowledge of chemistry is shit. Maybe there is one type of glue that is bad and one that is fine. Anyone know anything about this?