Evolution of the Runny Nose

So, for starters, if you're one of those people who pretends to be grossed out when people talk about certain subjects, I hate you. If you say, "Too much information!" a lot, I hate you. By the way, I don't know when it became acceptable to use "TMI!" as a joke. Someone will say, "TMI!" and, inexplicably, other people laugh. If you really aren't comfortable hearing something, say so in an adult way. Don't make people pretend to be amused when you pretend to be grossed out.

Now, why do our noses run in the cold? I'm not talking about actually having a cold, I'm just talking about walking around outdoors when it's cold out. I have three theories.

1. Actually, the runny nose is a by-product of extra tear production meant to protect the eyes. Warm tears help keep the cold temperature from damaging sensitive eye-tissue or something.

2. Same idea, but the fluid is meant to protect the nasal passages.

3. The fluid in the nose acts as a heat-exchanger. The body needs to conserve heat in the cold. Every time you breathe, you expel warm air and bring in cold air. Fluid in the nose heats up when you breathe out and then transfers this heat to the incoming air when you breathe in. This way the air entering the lungs is warmer than it would otherwise be, and energy is saved. Water would be good for this because it can spread out over the surface area of the nostrils and because it has a high specific heat (it takes a lot of energy to heat a given amount of it up by a given temperature, and likewise it releases a lot of energy when it cools).

Of course, all of these could be true at once, but my favorite is #3.