Why alcohol burns a cut

If, like most non-robotic megafauna, you've ever had the misfortune of cutting yourself, chances are that at some point you have poured alcohol on that bad boy to ward off infection.

Also included in the category "megafauna". In case you were feeling too pleased with yourself.

Chances are also high that you immediately regretted this decision, because it made what may have been a fairly minor pain a whole lot worse.

Despite how common this experience I'm describing is, not very many people know the reason behind it. Luckily, for the sake of this post, I am one of those people.

As you are probably aware, you have the ability to sense heat and cold.

This is because there are proteins on the surface of our cells called temperature sensitive channels. When you stick your hand in a fire, they're what tells you, "Hey! That's hot!" Let's get some perspective on where these things are in our bodies.

These channels open and close depending on the ambient temperature. The stuff that they then let in or out interacts with other proteins in your cells propagating the signal until it reaches someone that does something about it.

Now when you douse these channels with alcohol, speaking of the heat-responsive channels in particular, it changes how they respond to temperature. In essence, it lowers their "threshold", which we can think of as the temperature where it tells your cells to freak out. Alcohol puts that threshold so low that your own body temperature causes the channels to open! Thus it makes your body think that you're burning when really you're just existing.

There are other things besides heat (or lack thereof) and alcohol that affect these channels. Spicy food is described as "hot" for a reason--capsaicin, the active ingredient in peppers, binds to heat-sensitive channels and activates them. A common side effect of menthol and eucalyptus oil is a cooling sensation, which you can probably surmise comes from activation of cold-sensitive channels.

Now you know why this stuff confuses your mouth so much.