(CNN) It's a pesky problem: As soon as you strap on your cloth face mask and head out the door, your glasses fog up.
But there's a simple fix for that, and it'll only take a minute or two. All you need is soap and water.
This advice comes from the medical journal Annals of the Royal College of Surgeons of England, courtesy of two doctors. And if their defogging trick can work in the emergency room, it can certainly work in the grocery store.
Remember, scrub for 20 seconds (two rounds of "Happy Birthday") before you rinse.
There's no time limit for lens scrubbing, so be gentle and thorough.
Don't leave any soap suds on your lens -- if the fog didn't obstruct your vision, bubbles certainly will. They're not fun to rinse out of your eyes, either.
Avoid using a towel that may scratch your delicate lenses.