sore throat after long backpacking trips?

yea.. my remedy is to create as many new nonsense threads on BPL as I can.. very soothing

Mouth breather, or allergies? Other than that never heard of this,

Post nasal drip + cold, dry air maybe. LOL at Jason G ; ).

Same thing happens in airplanes. I think it's the dry air. Solution is to breathe humidified air at lower elevations—or get out of the airplane.

I breath through my mouth…

If no one else has heard of it I'll just talk to my doc… most of these things are common so maybe it's just me.

Yup dry air, plus at least partly mouth breathing. Prolonged exertion in low humidity gives me a painful sore throat. Don't have much experience at altitude but the little I do have suggests higher elevations exacerbate the problem.

ETA: Hard candy or throat lozenges help. Honey too, if you ever take it.

I know any time I'm out overnight and it's chilly (and in Alaska, that's most nights even in the middle of summer) I wake up puffy and hoarse with a runny nose. It's been a while since I've done more than a weekender and I can't recall now whether that went away after a few days or not. In your case, it sounds like it doesn't show up for a few days.

"Prolonged exertion in low humidity gives me a painful sore throat."
"mouth breathing"
I would agree with this.

"ETA: Hard candy or throat lozenges help. Honey too, if you ever take it."
Honey works wonders for a sore throat. Just ask my grandma.

I have the same thing happen to me. Not sure why, but it happens pretty consistently.

Does it matter whether you breathe through your nose or your mouth?

Yes it does.
Nature gave us a filtering system called a nose. The nose helps to regulate the volume or air we breathe. The nose cleans, warms and humidifies the air preparing it for the lungs. The mouth can do none of this. If you breathe through the mouth there is a drying of saliva leading to an increase of bacteria in the mouth and throat which can lead to gum disease, tooth decay and sore throats

Google search .(1.3 SEC)

and if one is not already in fantastic shape, yes, it will happen.
just as if one is starting out a new (and brutal) workout regime, it's going to be a few weeks before you feel like you don't have a "cold".
new to distance running ? ? = same thing.
Frank is probably right, in it's being bacteria.
i don't know the mechanics of it, but a really good romp + not being in stellar condition = fun and a sore throat.

once you are in decent shape, and you are making enough horsepower to hurt yourself, and beginning to enjoy it, that is when you will be loading your system hard enough to make your throat hurt. it's all good.
it happens reliably enough that i keep a bottle of listerene in the car to deal with it. (helps a great deal to hit it early)

i ordered your e-myth book.

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Bacteria on your hose mouthpiece, bike bottle spout or bottle top will eventually give you a sore throat. Turkey hunters have this problem if they don't sterilize their mouth calls after use.

Spelt nailed it. I have the same trouble at times too. Aggravated by allergies that plug up my sinuses and force me to breathe through my mouth.