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What are the causes of asthma? What are some examples of environmental pollutants that can trigger asthma attacks? Children at Risk Asthma is the most common chronic disease among children - especially children who have low birth weight, are exposed to tobacco smoke, are black, and are raised in a low-income environment. Most children first present symptoms around 5 years of age, generally beginning as frequent episodes of wheezing with respiratory infections. Additional risk factors for children include having allergies, the allergic skin condition eczema, or parents with asthma. Young boys are more likely to develop asthma than young girls, but this trend reverses during adulthood. Researchers hypothesize that this is due to the smaller size of a young male's airway compared to a young female's airway, leading to a higher risk of wheezing after a viral infection. Allergies Almost all asthma sufferers have allergies. In fact, over 25% of people who have hay fever (allergic rhinitis) also develop asthma. Allergic reactions triggered by antibodies in the blood often lead to the airway inflammation that is associated with asthma. Common sources of indoor allergens include animal proteins (mostly cat and dog allergens), dust mites, cockroaches, and fungi. It is possible that the push towards energy-efficient homes has increased exposure to these causes of asthma. Tobacco Smoke Tobacco smoke has been linked to a higher risk of asthma as well as a higher risk of death due to asthma, wheezing, and respiratory infections. In addition, children of mothers who smoke - and other people exposed to second-hand smoke - have a higher risk of asthma prevalence. Adolescent smoking has also been associated with increases in asthma risk. Environmental Factors Allergic reactions and asthma symptoms are often the result of indoor air pollution from mold or noxious fumes from household cleaners and paints. Other indoor environmental factors associated with asthma include nitrogen oxide from gas stoves. In fact, people who cook with gas are more likely to have symptoms such as wheezing, breathlessness, asthma attacks, and hay fever. Pollution, sulfur dioxide, nitrogen oxide, ozone, cold temperatures, and high humidity have all been shown to trigger asthma in some individuals. During periods of heavy air pollution, there tend to be increases in asthma symptoms and hospital admissions. Smoggy conditions release the destructive ingredient known as ozone, causing coughing, shortness of breath, and even chest pain. These same conditions emit sulfur dioxide, which also results in asthma attacks by constricting airways. Weather changes have also been known to stimulate asthma attacks. Cold air can lead to airway congestion, bronchoconstriction (airways constriction), secretions, and decreased mucociliary clearance (another type of airway inefficiency). In some populations, humidity causes breathing difficulties as well. Obesity Overweight adults - those with a body mass index (BMI) between 25 and 30 - are 38% more likely to have asthma compared to adults who are not overweight. Obese adults - those with a BMI of 30 or greater - have twice the risk of asthma. According to some researchers, the risk may be greater for nonallergic asthma than allergic asthma. Pregnancy The way you enter the world seems to impact your susceptibility to asthma. Babies born by Caesarean sections have a 20% increase in asthma prevalence compared to babies born by vaginal birth. It is possible that immune system-modifying infections from bacterial exposure during Cesarean sections are responsible for this difference. When mothers smoke during pregnancy, their children have lower pulmonary function. This may pose additional asthma risks. Research has also shown that premature birth is a risk factor for developing asthma. Stress People who undergo stress have higher asthma rates. Part of this may be explained by increases in asthma-related behaviors such as smoking that are encouraged by stress. However, recent research has suggested that the immune system is modified by stress as well. Genes Genes linked to asthma also play roles in managing the immune system and inflammation. There have not, however, been consistent results from genetic studies across populations - so further investigations are required to figure out the complex interactions that cause asthma. Genetics may also be interacting with environmental factors. For example, exposure to the bacterial product endotoxin and having the genetic trait CD14 (single nucleotide polymorphism (SNP) C-159T) have remained a well-replicated example of a gene-environment interaction that is associated with asthma. Airway Hyperreactivity Researchers are not sure why airway hyperreactivity is another risk factor for asthma, but allergens or cold air may trigger hyperreactive airways to become inflamed. Some people do not develop asthma from airway hyperreactivity, but hyperreactivity still appears to increase the risk of asthma. Atopy Atopy - such as eczema (atopic dermatitis), allergic rhinitis (hay fever), allergic conjunctivitis (an eye condition) - is a general class of allergic hypersensitivity that affects different parts of the body that do not come in contact with allergens. Atopy is a risk factor for developing asthma. Some 40% to 50% of children with atopic dermatitis also develop asthma, and it is probable that children with atopic dermatitis have more severe and persistent asthma as adults. What are some examples of environmental pollutants that can trigger asthma attacks? Air pollution can make asthma symptoms worse and trigger attacks. Two key air pollutants can affect asthma. One is ozone (found in smog). The other is particle pollution (found in haze, smoke, and dust). When ozone and particle pollution are in the air, adults and children with asthma are more likely to have difficulty breathing. Ozone is often worst on hot summer days, especially in the afternoons and early evenings. Particle pollution can be bad any time of year, even in winter. It can be especially bad when the weather is calm without wind, allowing air pollution to build up. Particle levels can also be high: •near busy roads, during rush hour, and around factories •when smoke is in the air from wood stoves, fireplaces, forest fires or burning vegetation |