http://www.ultimate-guitar.com/news/..._about_u2.html
09.
The sunglasses aren’t just there to make Bono look like a rock star. The U2 singer says he has an allergy to salicyclates: “
That means I lose my voice or I fall asleep in the strangest places, like once on the lighting board for Sonic Youth, one of the loudest concerts in the world. And I get red eyes, which is one of the reasons I wear glasses.”