Theobromine is chemically related to caffeine and theophylline (an asthma medicine). It's the reason chocolate improves your mood and breathing. It is found in cocoa, chocolate, tea, kola nut. Dark chocolate contains more theobromine than light. Theobromine also is a mild diuretic and opens blood vessels.
Theobroma is the the name of the genus of the cacao tree, (which itself is made up of the Greek roots theo ("God") and broma ("food"), making chocolate the food of god.
FYI a quick help to open your lungs, if there is not emergency medicine handy, is a cup of coffee or can of caffeinated soda or some chocolate, assuming you're not allergic to chocolate.
More esoteric information: Chocolate also contains flavanols which have anti inflammatory and anti atherosclerosis properties.
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