If you’ve ever noticed that one nostril feels more clogged than the other during a cold, you’re not alone — and it’s not random.

Scientists have discovered that our bodies naturally alternate airflow between nostrils every few hours in a process known as the “nasal cycle.” This happens in healthy individuals, even when you’re not sick. One nostril handles the majority of airflow, while the other takes a break.

But when you’re congested, the nostril already on its “rest phase” can feel completely blocked. This gives the illusion of one-sided congestion — especially during sleep or when lying down.

The cycle is controlled by the autonomic nervous system, the same system that regulates heart rate and digestion. It ensures each nostril gets periodic downtime to recover and humidify incoming air efficiently.

Fascinatingly, right-handed people tend to breathe more from their left nostril during cognitive tasks and more from their right during relaxation. This subtle shift is even tied to brain hemisphere activity.

So next time one nostril feels stuffed, don’t panic. It’s likely just biology doing its job.

Breathing is never as simple as it seems.