Asthma is often triggered by which of the following?

Asthma is a chronic respiratory condition that can be exacerbated by various environmental factors, one of which is exposure to cigarette smoke. Cigarette smoke contains harmful chemicals that can irritate the airways, leading to inflammation and increased mucus production. This irritation can trigger asthma symptoms such as wheezing, coughing, shortness of breath, and chest tightness.

In addition to aggravating existing asthma conditions, cigarette smoke can also contribute to the development of asthma in individuals who have never been diagnosed with the disease. Therefore, avoiding cigarette smoke and other sources of air pollution is crucial for individuals with asthma to help manage their symptoms effectively.

The other options, while they can influence respiratory health, do not have the same immediate and well-documented impact on asthma triggers as cigarette smoke does. High altitudes can present challenges due to decreased oxygen levels, low temperatures may lead to bronchoconstriction in some individuals, and excessive hydration does not typically have a direct correlation with asthma triggers.