There are a number of airborne allergens that come from various sources in nature, and it can cause the person to suffer from cold-like symptoms and red, itchy eyes. The causes include pollen, trees, plants, grass, weeds, ragweeds, hay fever, pine tree pollen, oak tree pollen, birch trees, Bermuda grass, St. Austine grass, Lantana plants, poison oak, mold spores and chrysanthemums.

However, there are ways to reduce airborne allergens. For instance, a person may want to stay indoors during the peak pollen and hay fever seasons, caulk and seal windows and keep their windows and doors closed, as these airborne allergens float through the fresh air. In addition, people may want to bathe their pets regularly so they do not bring the allergens in with their fur.

There are also allergens that can become airborne, and that includes dust mites. These mites are microscopic and feed off of human dead skin cells. People can be allergic to these little pests, as their exoskeletons can cause the person to sneeze, cough and have a runny nose. To prevent this, people can purchase allergy free pillows and mattress covers, which will help a person sleep through the night.