The exact causes for the development of Asthma are currently under investigation. The condition results from an inflammation of the airways that causes constriction that reduces the ability of an individual to inhale. Severe asthma is the most serious form of the disease. Severe asthma is characterized by a persistent inflammation that almost never ceases. Almost 10 to 15 percent of people who have asthma are diagnosed with severe persistent asthma. The exact definition of the severe form of the disease varies depending on which guidelines are used for diagnosis. Severe asthma is a very serious disease because it cannot be easily treated with the same drugs and inhalers that are effective for less severe cases. Some patients actually require continual use of an inhaler in order to deliver anti-inflammatory medications to the airways. Other individuals do not respond at all to any type of treatment. Severe asthmatics might need a nebulizer, epinephrine injections or an oxygen mask. Patients that have uncontrollable symptoms that affect the pulmonary system in the body might require a physical air tube or mask that delivers oxygen directly into the lungs when needed. Severe asthma might result from a genetic predisposition to respiratory problems. There is also evidence that environmental factors such as volatile organic compounds (VOCs), particulate matter and other types of air pollution can contribute to the disease. Some individuals might develop asthma as a child that can then escalate into severe asthma over time if the asthma is not properly treated. The onset of severe asthma can sometimes result from an illness or injury that affects the lungs. There is speculation that severe asthma is actually a completely different form of asthma and not just a more serious version of the same disease. Patients with severe asthma often have the inability to fully exhale the air that is taken into the lungs. Many severe asthmatics are also shown to still have inflammation and obstructions in the airways even after a treatment has been successfully applied. These factors can potentially contribute to the development of a different type of medication that can effectively treat severe asthma.