How does asthma differ from copd?

Asthma vs COPD : There is significant overlap. COPD is usually less reversible and caused by scarring due to smoking in most cases, where asthma is often allergic in cause. New evidence suggests maybe the smokers who get COPD were people with mild undiagnosed asthma, and some asthma patients don't reverse well at all! Some patients carry a dual diagnosis, and the medications used are often the same. Good Question