Like many chili-heads, I've long believed that capsaicin's
greater solubility in alcohol than water meant that you
should drink beer to help you deal with the pain of spicy
food. Harold McGee says no:
What about quenching the burn once the mouth is already on fire? The two surest remedies--though they're only temporary--are to get something ice-cold into the mouth or something solid and rough, rice or crackers or a spoonful of sugar. Cold liquid or ice cools the receptors down below the temperature at which they are activated, and the rough food distracts the nerves with a different kind of signal. Though capsaicin is more soluble in alcohol and oil than it is in water, alcoholic drinks and fatty foods appear to be no more ffective than cold or sweetened water at relieving the burn (carbonation adds to the irritation). If all else fails, take comfort in the fact that capsaicin pain generally fades within 15 minutes.
This and this appear to be the relevant citations. Unfortunately, these are only abstracts; see here for a review article.
I've always found sugary, cold drinks to be the thing to help with spicey foods when one has bitten off more than they can chew. I have no science to back this up... just a personal observation.
Yogurt or sour cream for me.
Sugars react with capsaicin to neutralize its heat, at least according to Alton Brown. The Scoville measure of chili heat used to be based on this concept. The trouble with many alcoholic drinks is that they're acidic, and so as TFA points out, they tend to increase the pain/irritation. I find iced tea (sugared but limited lemon) to be a very effective abatement measure -- sugary plus icy.
Tell me again why we're trying to reduce the heat?
Enjoy the burn, baby.