Many people with eczema (also called atopic dermatitis) know that genetics, allergens, and stress can play a role in this condition. Those with eczema have an overactive immune system and a compromised skin barrier that causes them to develop scaly, itchy, inflamed skin in response to substances found indoors or outdoors. There are also other risk factors for the development of eczema and its itchy flare-ups, such as where you grew up and where you live now.
For years, scientists have theorized that geographic area and living conditions may influence the development of pediatric eczema, as well as other allergic diseases like asthma. The studies on this subject do not always agree, however, and more research needs to be done to make definite conclusions.
Some dermatology research (even large epidemiological studies) shows that environmental conditions including weather, pollution, and urban or rural settings can bring on eczema in childhood or protect against its development. These same factors can influence how severe your eczema will be, how often, and when you experience flare-ups.
Sudden changes in weather and living in drier climates are two risk factors that make it more likely that your child may develop eczema or experience flare-ups. You may also experience more frequent or severe flare-ups under these conditions as an adult.
“I’ve noticed that when the weather changes, my symptoms get worse. Heat and cold also cause flares,” said one MyEczemaTeam member.
Those who live in drier climates are at higher risk for eczema because the dry air takes moisture from the skin, leaving it with small cracks. These cracks make the skin more sensitive to substances in the environment, such as allergens and toxins. As a result, the skin can become brittle, itchy, rough, tight, and scaly, and may even bleed, leading to eczema flare-ups. If you also have sensitive skin or a predisposition to allergic disease, you may be at high risk for eczema in these weather conditions.
A windy or cold climate that dries the skin can also lead to eczema flare-ups. These weather conditions sap the skin of moisture and may bring on eczema flare-ups or cause eczema to be more severe. In these climates, people also spend a lot of time indoors in the winter, where the hot air from heaters is dry and further takes moisture from the skin. At the same time, weather that is hot or humid may cause skin irritation, and bring on itching and rash.
A large survey-based study of more than 91,000 children in the United States, ranging in age from infancy to 17 years, found that the incidence of severe eczema was highest in children living in the Northeast or Midwest. The scientists noted that areas with lower humidity, lower ultraviolet index (the measure of the sun’s radiation), lower temperatures, and more precipitation increased the risk for severe eczema.
The Northeast and Midwestern states have low humidity outdoors during the winter, and the increased use of indoor heating also decreases moisture in the air. As a result, skin dryness and contact dermatitis can develop in people at risk for these conditions, the researchers said.
Many studies have found that the incidence of eczema and other allergic diseases is higher in urban areas, and the incidence has increased most dramatically in the last 40 years, as many countries have become more industrialized. One Swedish study that looked at four groups of children born between 1952 and 1981 found that urban and rural areas showed an increased incidence of asthma and eczema after 1970. Yet urban living increased risk to a greater degree than residing in a rural community.
Still, the United States study of 91,000 children did not find that those living in cities had more severe eczema. More serious skin disease and flare-ups were instead linked to dilapidated housing and living in neighborhoods where there was garbage on the streets.
Children who grow up on farms tend to have lower rates of allergic disease such as eczema, but the reason is not well understood. Scientists have speculated that children who live on farms are exposed to a wider range of bacteria, which influences the development of their gut microbiome (the array of microbes or germs in the intestines).
Some researchers point to these rates as support for the hygiene hypothesis, a theory that suggests the rates of atopic dermatitis will go up as our society becomes cleaner and children are not exposed to as much bacteria.
Bacteria in the gut that digest fiber produce short-chain fatty acids that are thought to be important in preventing disease. A few studies have found that children living on farms who did not develop eczema had higher concentrations of several short-chain fatty acids in their feces.
Some research has also linked exposure to traffic-related air pollution (TRAP), particularly truck traffic, to the development of eczema, asthma, and allergic rhinitis in early childhood and symptoms throughout life. Researchers believe that TRAP is one of the reasons why the incidence of asthma, eczema, and other allergic diseases have increased worldwide since the 1960s.
In large North American cities, close to 45 percent of people live in areas that have high exposure to TRAP. Thirty percent of schools are located in neighborhoods with high levels of TRAP. A 2015 systematic review of studies on traffic pollution and allergic diseases found that higher levels of air pollutants, including those generated by traffic, are associated with the development of eczema in childhood. High exposure to pollutants generated from traffic is especially harmful in the first four years of life and increases the risk of sensitivity to airborne allergens, leading to diseases such as eczema, by 40 percent to 83 percent.
Although urban living can predispose people to develop eczema and flare-ups, those who live in cities that are more industrial and with more traffic are most at risk. A questionnaire-based study of 8,334 adolescents ages 13 and 14 living in five Canadian cities — Vancouver, Saskatoon, Winnipeg, Hamilton, and Halifax — found that the prevalence of atopic eczema was significantly higher in Winnipeg and Vancouver than in the other three cities.
Winnipeg is known as a transportation hub within Canada, and Vancouver is the major urban center of Western Canada — a major trade and transportation center. Other than residence in these cities, the researchers found that heavy exposure to traffic exhaust was associated with a higher prevalence of eczema.
Yet other studies have found no link between air pollution and allergic disease. In a comprehensive meta-analysis published in 2020, researchers assessed children at ages four and eight who were previously enrolled in five different cohort studies living in seven areas of five European countries. When they compared eczema rates in these children to the outdoor levels of two different kinds of pollutants generated by traffic, they found there was no association between higher pollution levels and the prevalence of skin disease. They also found that TRAP played no role in the development of asthma and rhinoconjunctivitis (allergies that affect the nose and eyes) in children.
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Do you think where you grew up (or where you live) may be a factor in your eczema? Share your experience in the comments below, or start a conversation by posting on MyEczemaTeam.