Question: What are perfumes made of?

Eoin McKinney answered on 15 Nov 2017:

If a chemical changes easily from a liquid into a gas we call it ‘volatile’. When the molecules become a gas they can reach our nose where special cells recognise them. We find some chemicals pleasant (like flowers) and this has been used by perfume makers. They basically hunt for mixtures of chemicals that are volatile (so we can smell them – if a liquid doesn’t release chemicals it won’t smell of anything!) and that smell nice. The reason people put perfume on the wrist and neck is because these are supposed to be ‘warm’ areas where the heat will turn the liquid into gas so you can smell it more easily (and they are exposed so the molecules can get out to reach other peoples noses!). The same process goes for bad smells – we detect them in the same way but have evolved to think they’re unpleasant. We probably find dirt and toilet smells unpleasant to make us avoid them and so reduce our chances of infection – it was a long time before any learned about germs but we have been avoiding bad smells for much longer because we don’t like them!