What is a humidifier? Humidifier therapy adds moisture to the air to prevent dryness that can cause irritation in many parts of the body. Humidifiers can be particularly effective for treating dryness of the skin, nose, throat, and lips. They can also ease some of the symptoms caused by the flu or common cold. However, overusing humidifiers can potentially worsen respiratory problems. It’s important to know how to use them correctly, so, make sure to check this video.