Sinuses are the hollow cavities in the skull lined with soft tissue called the mucosa. They have a thin layer of mucus that moisturizes the inside of the nose. This mucus then shields the nose from dust, dirt, microbes, and other pollutants. Healthy sinuses humidify and filter the air we breathe in which ensures that the kidneys, lungs, and blood stay safe from toxin invasion. The presence of toxins in these two organs can lead to infections, such as a sinus infection. These are the functions sinuses perform under normal conditions.