Indoor humidity levels are an important factor in keeping allergy symptoms at bay. If the indoor humidity is above 50%, it can encourage dust mites, cockroaches and even mold growth. These potent allergy triggers can be greatly reduced if humidity is kept below 50%. A home dehumidifier can help lower indoor humidity levels. When indoor humidity is too dry, less than 30%, it causes dry nasal passages, skin and throat which can be troublesome for many people. Air that is too dry will cause dust mites, mold and bacteria to dry out and become airborne which could be inhaled. Using a home humidifier can help bring humidity levels up to the optimum range which is between 40-50%. Keeping home air levels within the recommended range will greatly reduce allergy symptoms for most allergy sufferers.