Why Morning IS BEST for Smell Tests

The idea that morning is best for a "smell test" stems from how your olfactory system—your sense of smell—operates throughout the day. When you wake up, your nose is   typically at its most rested and least overwhelmed state. Overnight, while you sleep, your exposure to strong odors, pollutants, and other sensory inputs drops significantly. This gives your olfactory receptors a chance to reset, making them more sensitive to new smells in the morning.

During the day, your nose encounters a barrage of scents—food, exhaust, perfume, you name it. This constant stimulation can lead to olfactory fatigue, where your brain starts tuning out or dulling your perception of smells to avoid overload. Think of it like background noise you eventually ignore. By morning, after hours of minimal input, that fatigue has worn off, and your sense of smell is sharper, more attuned to picking up subtle differences.
There’s also a circadian rhythm angle. Your body’s internal clock influences all sorts of functions, including smell. Studies—like one from Brown University a while back—have shown that olfactory sensitivity peaks in the early morning hours for many people, aligning with when your body is naturally waking up and gearing up for the day. It’s not a huge leap to say this could make morning the prime time for something like a smell test, where clarity and precision matter.
Plus, practical stuff: you haven’t eaten breakfast yet, so no coffee breath or garlic from last night’s dinner lingering. Your nasal passages might also be clearer if you’ve slept well, assuming no allergies or colds are gunking things up. All this adds up to a cleaner slate for your nose to do its job.