Besides the musty odor and visual blight, mold and mildew can cause a wide range of health effects. Mold allergies, for instance, can be a nuisance to people all across the nation, but research shows that some people have it worse than others. Do you live in a city with a mold allergy problem?

Our list of the five worst cities for mold allergies combines research from four different ranking reports. The first was a 2011 Quest Diagnostics report called Allergies Across America, which was the largest study of allergy testing in the United States. The study’s results revealed allergy sensitization rates for five different kinds of allergies (food, common ragweed, dust mites, mold, and pets) in 30 of the largest cities in the U.S. The second was a 2006 report by the Allergy and Asthma Foundation of America, which ranked the “asthma capitals” of the U.S. We also used a 2008 Centers for Disease Control list of the healthiest cities in the country and a 2011 Men’s Health ranking of the nation’s most active cities.

What Is Mold?  What Are Mold Allergies?

Mold is a kind of fungus that can grow almost anywhere, on any surface, as long as moisture and organic material are present.  Although there are certain kinds of toxigenic molds that can cause serious, long-term respiratory problems (so-called “black mold” or Stachybotrys, among others), the vast majority of mold varieties are harmless in small quantities. However, even normal, healthy people can have mold allergies when it festers inside a home. Patches of mold release tiny spores—invisible airborne mold particles—which can be inhaled into a person’s lungs.

toxigenic mold allergies

These spores can trigger asthma attacks and are a common cause of allergy symptoms, including throat irritation, coughing, wheezing, sneezing, itchy eyes, headaches, sinus pressure, drowsiness, and fever.

Allergic sensitivity is on the rise in the United States. Ragweed and mold allergies in particular are becoming more common as a variety of factors contribute to increased pollen counts and excessive mold growth. Environmental influences play a role in the mold sensitivity of certain regions, meaning that mold allergies are more prevalent in some cities than in others. Below, we’ve listed five of the cities that suffer the most from mold allergies:


Everything is bigger in Texas—even mold allergies. According to our ranking system, the worst city in America for mold allergies is none other than Dallas, Texas. Quest Diagnostics’ report listed Dallas as the city with the highest mold sensitization rate, at 21%. This means that of the hundreds of blood samples of Dallas residents, 21% showed an allergic reaction to mold. Dallas also holds the top spot in the overall allergy sensitization index. The state of Texas has a long history of mold-related problems. In 2001 a resident of Dripping Springs, Texas, Melinda Ballard, sued her home insurance company for mold damage to her mansion, initially receiving over $32 million in damages. The case was highly publicized in the national media and is widely credited with starting a Texas-sized mold lawsuit stampede. In the decade following the Ballard case Texas led the nation in mold litigation and lawsuits.


Phoenix, Arizona comes in number two in our rankings system. In the Allergies Across America report, Southwestern and Midwestern cities ranked significantly higher than cities in other parts of the country. The mold sensitization rate of Phoenix (19%) and its overall allergy sensitization index (695) appears to follow this overall trend.  Another factor contributing to Phoenix’s ranking is the city’s asthma rates. In 2006 the Asthma and Allergies Foundation of America ranked the Phoenix-Mesa area as the 18th most challenging metropolitan area for asthma sufferers.


Windy City residents ought to let a little more fresh air into their homes, as Chicago comes blowing in at number three in our moldy cities ranking. Chicago is listed here for three main reasons. First, it’s located in the Midwest, which has seen a substantial rise in mold allergies and ragweed allergies over the past decade. Second, the city of Chicago is located on the shores of Lake Michigan, which, along with blizzard and rain conditions, leads to a very damp climate. And third, the city is ranked as the 22nd worst city in America for asthma sufferers. Chicago also ranked a dismal 123 out of 184 in a 2008 Centers for Disease Control list of the healthiest cities in America.

Riverside-San Bernardino

Riverside, California, located north of San Diego and east of Los Angeles, actually has the second highest mold sensitization percentage (20%) of the 30 cities in the Allergies Across America study. Its overall allergy sensitization index is lower than that of either Chicago or Phoenix, though, but still ranks well above average. Additionally, the San Bernardino-Riverside-Ontario metropolitan statistical area ranked below Chicago at 127 out of 184 in the CDC list of the healthiest cities in the U.S.

Los Angeles

Located about an hour’s drive from San Bernardino, the city of Los Angeles comes in at number five in our list of moldiest cities. Even though Tinseltown has a relatively healthy population and is ranked in the middle of the pack when it comes to asthma prevalence, it still has a mold sensitivity level of 17% and an overall allergy sensitization index of 660. One of the good things about living in L.A. is that the weather stays comfortable and relatively dry year-round, helping to fight moisture and dampness levels that cause mold growth. 

Full Moon Above Denver

Honorable Mention: Denver

Denver, Colorado ranked eighth in our mold allergies scale, but certain factors make the residents of Denver particularly susceptible to the dangerous effects of mold allergies. Denver had a 16% mold allergy sensitization rate, which is roughly the same as other Midwestern cities, like St. Louis, Kansas City, and Minneapolis-St. Paul—well above average for the top 30 cities in the United States. 

The thing that makes Denver stand out from the pack is the fact that the state of Colorado does not recognize standard renter’s rights when it comes to moisture, leaks, and mold that results from property damage. Denver renters who have mold in their homes have little legal recourse for fixing the problem. Of course, Denver ranked in the top ten of the healthiest cities list, so residents of the Mile High City get more fresh air than the ones mentioned above.

Pofessional mold experts can set up containment chambers and effectively remove mold problems without exacerbating any existing allergy problems.

Who You Gonna Call?

Even though some cities have a higher rate of mold allergies than others, mold can grow anywhere, and any person—no matter how healthy—can suffer from the symptoms of mold exposure. Whether you live in a city with a high mold allergy sensitivity rate like Dallas or the city with the lowest sensitivity rate, Seattle (7%), it’s important to have your indoor air quality tested by a professional. Mold inspection companies with certifications through the Indoor Environmental Association (IEA) can conduct air and surface tests with lab results to determine if your home contains a harmful level of mold, allergies, or dust mites.

If you think you are experiencing mold allergies or if you know you have a mold problem in your home, take the proper steps to fix the situation. After hiring a specialist to test for mold, have the mold remediated and the underlying cause of the mold repaired. Attempting to clean mold by scrubbing with household products will oftentimes make matters worse. Aggravating the mold site will cause it to release even more particles into the air. If you take these steps you will live a healthy, mold-free life wherever you live.