A few months ago, a TikTok video claimed that 85 percent of people can only breathe out of one nostril at a time. So, is this true? 

Rachel Roditi, M.D., section chief for the Division of Otolaryngology at Brigham and Women’s Hospital in Boston, Mass., explained to Men's Health in 2016 that nostrils actually take turns in switching off the duty of breathing air in and out.

She also explained that this process can happen between every 90 minutes to four hours.  

This cycle also explains why people tend to feel more congested in one nostril more than the other. Dr. Roditi noted that our noses funnel resources to one side to increase efficiency, which causes more blood to flow to the dominant nostril. If you're feeling sick, that blood flow will increase, which leads to more swelling and the production of mucus.

Therefore, though you are congested in both nostrils when feeling under the weather, it may feel greater in the nostril that is dominant because it is already swollen due to the typical nasal cycle.