Humidifiers can help or hinder allergies, depending on where you live and how they’re used. The right humidity levels, which fall between 30 to 50 percent, can help prevent some particulates from entering the breathable air. The right humidity levels also prevent dryness of the nasal passages, airways, and throat, which can alleviate allergies. However, if the humidifier releases too much humidity, it can promote mold and mildew growth, which can worsen allergies.