Ceasing to smell one’s perfume after constant exposure while people walking by can still smell it is just one case of a phenomenon called olfactory adaptation. A similar fading of odor signals with continuous exposure also happens in animals, and scientists often depend on animal studies to try to understand the cellular and molecular bases for the condition. This is useful because it allows animals to sort out the indications of a new odor from the background noise of constant odors. It may also permit them to sense when an odor grows stronger. An identified chemical that acts as a gatekeeper for neurons involved in smell, opening and closing their electric signal channels. Genetically engineered mice that did not produce the substance, a protein called CNGA4, had profoundly impaired olfactory adaptation. A separate test-tube study found similar changes on a cellular level, with the signal channels remaining open when CNGA4 was absent. Hopefully this research will one day allow people to not forget the smell. The mice do not produce CNGA4 so they can handle it. Maybe one day after more genetically testing people will be able to smell fine all day without reapplying multiple times and eventually having it to be overpowering to others.