Chocolate as an Aphrodisiac

Chocolate contains three substances, caffeine, theobromine and phenyethylamine which together give people the impression that it is an aphrodisiac.

Caffeine acts as a stimulant, which may increase arousal or interest.
Theobromine stimulates the heart muscle and the nervous system further increasing arousal and interest.

Phenyethylamine may work as a mood elevator and an anti-depressant.

The combination of these three substances gives you the impression that chocolate is an aphrodisiac. Whether or not it actually works is up to you.