Many or perhaps all of the smells produced by your body are produced by the bacterial ecosystems living on and in you. Some of these smells are things we can detect; others we're unaware of. Certain strains of skin bacteria attract mosquitos. By altering the ecosystem on our skin, we can repel mosquitos. Cool!
With genetic engineering, we can do even more. We can replace the bacteria that turn sweat into unpleasant smells with bacteria that turn sweat into floral scents! No more deodorant!