Bugs can fly into my mouth when I am riding. Can you recommend a biker's mask or something to avoid eating bugs?

P.S.: I can't ride with my mouth closed since my nose is always full plus I've got asthma.

Well I'd advise to keep your pie hole shut but the asthma thing...
If I'm in a buggy area I use a bit of an overbite look to breathe without inhaling bugs...usually works fine.
Where the heck are you riding where it's that buggy?
I'm in Northern NY in dairy country with hay and cornfields everywhere as well as Lake Ontario and the St. Lawrence just down the road but I generally get schmaybe one buy per season.

we don’t have many bugs out here, but i find keeping my head down a bit (also more aero) prevents the majority of them from impacting my eyes, face, mouth.

i also can’t breathe through my nose, at all.

Took a bee to the lip at 35 mph. It's last act was to sting me before it spattered across my teeth. Bitter.

There are some seasons and some times of day that I find a ton of something smaller than bees but larger than 'skeeters are all along Canada Rd, especially in the spots with trees on both sides of the road. That's when I, as they say, "Grit my teeth and think of Mother England".

Neck gaiter pulled up when in bug country.
Pro tip: Will not help much with pigeons under freeway bridges.

The knats in the woods I mt. bike can do at least 7mph, but not 8 or above, I found out Thurs.

Just chew them up. Dragon flies are nasty tasting though. Hurt too when they hit you in the face at 30 mph.

For bees and wasps, bite quickly.

Years ago a group of us were doing a training session for a team time trial along a road that borders the St Lawrence river. At that time there were thousands of large flies along the route. One of the team took a long, long pull and as he moved to the back he told us "OK your turn, I'm full"

Nope. Eating a bug occasionally is a fact of life for riding bikes. The more bugs in the air, the more risk you have of ingesting them. You could kludge up a screen in a cut-out surgical mask, but the social approbation would probably be more than you could take.

I took in I think a honey bee yesterday. It sat against my tongue just behind my teeth, its side to my tongue. I spat/blew it out right quick. No sting and I never saw it but both the size and fuzz said honeybee. I think we both came out unharmed (and I do not take bee stings well). No fear here but I stepped on one as a kid and couldn't fit a shoe for days.

Don't know where you ride, but I find there's some places near me where the bugs are thick and others where you never encounter any.

Maybe change where you ride?

Except for anti-maskers, a lot of us have been wearing different types of mask in the past two years. You can certainly wear it cycling.

Oh-------------and be sure to use the tooth paste for cyclist---------------Bug Out!!!!!!

Mesh tube mask is a very good option. I think it's also called a "mesh neck gaiter" or "mesh buff", "Tactical/army neck gaiter/balaclava", among others.

Extremely breathable even when wet and offers some UV protection over your neck too. It seems to filter out some of the soot from diesel exhaust as well.

Look something like this:

As a doctor, I would think you’d be up on the latest mask technology.

A mesh tube as shown above is a good option or one of those TT helmets with a face shield could work nicely. I luckily don't live near a bunch of bugs so I can breathe easier when my nose is stuffy or having other issues.

Eat 'em. That's what Bill Gates & the UN wants us to do...

Sorry, couldn't resist.

On a serious note, you could check out this. It is an add on to your helmet, which lets you have a full visor on any helmet, according to their claims. It's on Kickstarter now. https://www.kickstarter.com/projects...rs?ref=popular

The only bugs that I don't like are bees, wasps, yellow jackets, etc. Flies, horseflies, june bugs, gnats don't bother me. I hit a carpenter bee last year and it felt like a bird hit on my helmet. As far as protection, uh, well, I keep my head down and try not to ride with my mouth wide open.

Maybe something like this?

Una mosca non vola dentro una bocca chiusa.

I would look for a piece of fine mesh you can easily breath through that you can tie behind your head bandit style.