Now here’s an interesting study, as reported at Science Blogs :
The smell of sweet odors helped participants withstand discomfort. Apparently, smelling something sweet specifically increases pain tolerance. Scientists compared three groups, exposing each group to a different smell (sweet, pleasant but not sweet, and unpleasant – civet musk). What’s interesting is that a sweet odor did not actually reduce the pain, but merely the ability to withstand it. There’s likely nothing causal here, as the article points out. We’ve learned – or have been taught – to associate sweets with pleasure.
A marketing tidbit, apropros of sugar: bakeries and cookie shops and even some markets pump sweet scents through the air intentionally.