If you have asthma your airways always have some type of irritation. When you have an asthma attack, this irritation gets worse and your airways close part way and get blocked with mucus. Asthma attacks may include coughing, chest tightness, wheezing, and trouble breathing.
An asthma attack can occur when you are exposed to things in the environment, such as house dust mites and tobacco smoke. These are called asthma triggers.
Your personal triggers can be very different from those of another person with asthma. Try to avoid your triggers, such as the ones listed in this slideshow.
Environmental Tobacco Smoke (Secondhand Smoke)
Environmental tobacco smoke is often called secondhand smoke because the smoke created by a smoker is breathed in by a second person nearby. Parents, friends, and relatives of children with asthma should try to stop smoking and should never smoke around a person with asthma. They should only smoke outdoors and not in the family home or car. They should not allow others to smoke in the home, and they should make sure their child's school is smoke-free.
Source: US Centers for Disease Control and Prevention.