The urban jungle and allergy.

The urban forest is the assemblage of trees, shrubs, and other plants that occupy the urban and suburban zone. In urban areas, the number of potentially allergenic plants has grown rapidly as the diversity of plants increases. The recommended street trees of many cities are allergenic species that are well known to allergy clinicians. Some of the most commonly planted trees in urban zones are known to be the greatest producers of pollen. These trees are situated in close proximity to humans, either at home, at work, or on their travel routes between locations. There are common misconceptions about the plants that do and do not cause allergy. It generally has been considered that insect-pollinated plants with showy flowers are allergy safe; however, when these species are planted in close proximity to people, as they are in urban landscaping, the pollen that leaks from the flowers is often enough to cause an allergic reaction. With increasing emphasis on green space in urban areas, it is advisable to evaluate what is being planted, how much is planted, and the plants' potential for triggering allergy.