NasalGuard Allergen Blocker is a tube of gel that you spread around your lips and nostrils, and it's supposed to reduce airborne particles from entering your airways.

Billed as a "Personal Air Filter", it's described as drug free, safe, and invisible. You apply it every 3-6 hours, or as often as needed. One tube is said to provide about 200-225 applications.

They're also coming out with a variety just for blocking cold and flu viruses. I suppose you'll have to apply both tubes if you want total protection.

$9.95 from the NasalGuard website.