'Tape Face', of America's Got Talent fame, was likely unaware of the many health benefits of the funny skits he always performed with his mouth taped shut.
Did you know that "mouthbreathing... changes the physical body and transforms airways, all for the worse? Inhaling air through the mouth decreases pressure, which causes the soft tissues in the back of the mouth to become loose and flex inward, creating less overall space and making breathing more difficult. Mouthbreathing begets more mouthbreathing." This material was taken from the book 'BREATH' by James Nestor. It is an excellent read if you really want to delve into breath and breathing correctly.
There are many other issues that can be caused by mouthbreathing that range from poor dental health, dehydration, impaired athletic performance, snoring, mild sleep apnea, foggy thinking and the list goes on. Learning to breathe through your nose is one of the cheapest, easiest and most beneficial things you can do to improve your health.
We started the journey to stop mouthbreathing by ensuring we sleep with our mouths shut. Surgical tape can be used to help keep the mouth closed throughout the night. It can take some practice to keep the tape on all night if you have sinus issues, but, once you do, you will reap the benefits of a better night's sleep. Mouth-taping is often used to resolve snoring and mild sleep apnea. Opening up your sinuses is similar to working a weak muscle - the more you practice, the better your sinuses will perform. Here is an informative 23 minute video with more insight on mouth taping.