Introduction

• According to the American Lung Association, nearly 20 million people in the United States have asthma. Asthma can be caused by a variety of reasons. Allergens and toxins both play important roles with causing asthma and asthma flare-ups. However, habits, such as smoking, can also cause asthma and asthma flare-ups. This is even when you are inhaling second hand smoke, which is also known as passive smoking. Children are especially susceptible to having asthma as a result of passive smoking.
  
  

Cilia

• Second hand smoke has an effect on every part of your ability to breathe, starting with your airways all the way down to your lungs. One of the first lines of defense against damage from habits like smoking are the cilia. Cilia are small filters in your airways that trap dust and other allergens before they reach your lungs. All cigarettes, regardless of filter, contain tar. This tar easily coats the cilia each time you smoke. The tar covered cilia are then no longer able to filter the allergens and other irritants that cause the damage necessary to provoke asthma and asthma attacks.
  
  

Irritation

• Asthma often occurs when irritation of the windpipe causes the muscles around the airways to contract. This closes off the air to the lungs. The toxins inside even second hand cigarette smoke are almost all trachea irritants. This means that as you smoke, your body reacts to the cigarette smoke irritation by contracting the muscles around the windpipe and closing off air to the lungs. This is one of the first signs of asthma.
  
  

Mucus

• Second hand passive smoke can also cause asthma by increasing the amount of mucus in your airways and lungs. This can cause the lungs to swell and become narrow, making it difficult to breathe.