The metropolitan cities with alarmingly high allergy cases generally have three common factors: higher-than-average pollen count and allergy medicine usage and lower-than-average board-certified allergists per patient. People with allergies should leave out certain cities from their list when planning to relocate. If you’re prone to seasonal allergies and are looking to move to a new city, read on to know about the worst cities to live in for people with allergies:

• Knoxville, TN

  While Tennessee is a beautiful place to live in, it is known to have one of the highest pollen counts in the country, especially in Knoxville. One of the varieties, the Ragweed pollen, has been known to be allergic to almost 16 percent of all Americans. Knoxville’s pollen score is recorded to be worse than average, and the city brims with trees, plants, and grassy areas since it is located on the Tennessee river, leading to more pollen and allergens to be dealt with. Also, the place usually gets light wind and high humidity, and it has warm temperatures, which act as ideal conditions for the plants to bloom, further contributing to the pollen count. Plus, the city sits in the Tennessee valley, which traps the wind and pollen.

• Louisville, KY

  Louisville makes it to the top of the list of the country’s worst cities to live in with allergies due to two factors: geography and climate. The hills that border the city in both north and the south cause the air to trap allergens like pollen, which naturally disperse with the wind otherwise. Besides, the average rainfall and climate promote grass and weed growth, and bluegrass—found in abundance in Louisville—is known to produce more pollen than any other grass. Other factors like the city’s proximity to the river, it’s year-round smog ratings, and the humidity levels during the summer months add to its allergenic nature.

• Charlotte, NC

  The American College of Allergy, Asthma, and Immunology has estimated that around 30 percent of the adults in Charlotte have nasal allergies, which has pushed the city on the list of the worst cities to live in for people with allergies. The Head Immunologist and Allergist at the institute says that the abundance of trees in the city, which makes it aesthetic and beautiful, can serve as a downside by increasing the frequency and effects of pollination, which elevates the chances of allergies stemming from them.

Approximately 50 million people in the country suffer from some kind of allergy on a regular basis, and half of these cases are seasonal allergies. Allergic reactions in the Southern states mostly result from a variety of allergy-producing trees that get more light and humidity for a major part of the year, increasing pollination.