Snorting salts is Bono's own way of hitting the high notes.
The singer's fellow Irishman Danny O'Donoghue from The Script, has said that snorting salts is just a trick to improve high notes.
"Snorting salts or white powder - it's actually a singing technique," The Mirror quoted him, as saying.
He added: "Myself and Bono share a vocal coach. Whenever the high notes aren't feeling that high or in the morning you're groggy, you snort salt water up your nose.
"It cleans out cavities, it's a natural antiseptic for your throat."