- Allergies and sensitivities
Allergies underlie many cases of asthma. An allergy is an inappropriate immune response against an innocuous compound. A wide variety of environmental allergens can cause an asthma attack, including food allergies. For those whose asthma is associated with environmental allergies, immunotherapy (e.g., “allergy shots” or sublingual immunotherapy) may help prevent exacerbations. In the case of food sensitivities, experimental research suggests that chronic, low-level inflammatory reactions triggered by an immune response to food particles may set the stage for airway inflammation. Some evidence suggests that IgG antibody testing is able to detect immune reactions less severe than an overt allergy, but that nonetheless may trigger inflammation.
Studies have consistently shown a relationship between smoking and asthma. Smoking is also related to decreased asthma control, higher risk of asthma attacks and death. Improvements in lung function and asthma symptoms have been observed among those who quit smoking.
Occupations commonly associated with asthma include woodworking, detergent manufacturing, some health care professions and baking.
A variety of common viral infections acquired during infancy and early childhood appear to increase the risk of childhood wheezing episodes that may eventually lead to asthma. In contrast, other evidence suggests that childhood exposure to microbial pathogens and foreign peptides may protect against the development of childhood asthma – a theory known as the hygiene hypothesis.
Certain medications, including non-steroidal anti-inflammatory drugs (NSAIDs) and ACE-inhibitors can trigger an asthma attack in some people.
Exercise can trigger asthma exacerbations, so people with asthma should exercise with caution (NHLBI guidelines). Other medical conditions commonly associated with asthma include chronic rhinitis, chronic sinusitis/rhinosinusitis, gastroesophageal reflux disease (GERD), obstructive sleep apnea, chronic obstructive pulmonary disease (COPD), hormonal disorders, obesity, depression and anxiety.
Stress is associated with asthma as well. These conditions may share some pathophysiological mechanisms with asthma and may influence its expression. Associated diseases may also influence how a patient with asthma responds to treatment. Likewise, the asthmatic condition and the inflammatory processes in asthma may influence how these associated conditions develop or progress over time.