So, in more layman’s terms, olfactory fatigue occurs such that when you sense a specific odor, the receptors associated with that molecule can no longer be stimulated by similar molecules because the channels that create the electrical impulse will ultimately close. The result leaves only receptors that get stimulated by other molecules (different types of odors)- thus, your propensity to sense new smells more strongly, and the ones you get consistently bombarded with eventually no longer being detected at all. Congratulations, you’re now nose-blind.
— Business Insider explains olfactory fatigue. Read more at Human beings can't smell themselves, even when they stink — here's why.