Why do we associate citrus smells with being clean?
Lemons were used in the past for household cleaning. The citric acid in the juice dissolves limescale and was used to bring the shine back to copper pans. Lemon oil, from the peel, was used in wood polish. When commercial detergent and cream cleaners became widely available, lemon oil was an easy way to add a pleasant scent that was already associated with cleaning. Nowadays, so many cleaning products use lemon and lime scents that we have become conditioned to link the smell with cleaning. In 2005, Dutch researchers found that citrus smells can cause us to keep our kitchen cleaner, by subconsciously putting the idea of hygiene in our minds.