The idea behind mouth taping is to force the body to breathe solely through the nose while we sleep. Why does this matter, you may ask? Well breathing through your nose helps to filter the air and deliver more oxygen to the body due to the production of nitric oxide in the sinuses. Because nitric oxide acts as a vasodilator, this causes more oxygen to be delivered and lowers blood pressure and increases blood flow which also can reduce inflammation.
In addition, mouth breathing has been linked to snoring and obstructive sleep apnea and also to halitosis. While not everyone needs to tape their mouth while they sleep, if you know that you breathe through your mouth predominantly, consider this cheap and effective health benefit and tape your mouth while you sleep.