Asthma is a condition in which the airways (or breathing tubes) of the lungs become inflamed and swollen, and produce mucus. The airways become narrowed and it is difficult to breathe through tiny airways so patients with asthma feel short of breathe, their chest feels tight and wheezy and they often develop a cough. The tiny muscles in the airways go into spasm and this makes the airways even narrower.
Many things can cause the airways in a person who has asthma to become swollen or twitchy. Some of these include viral infections like a common cold, particles in the air like pollen or house dust, cigarette smoke or cold air.
People with asthma tend to experience periods of feeling well, without any noticeable tightness or wheezing, interspersed with periods of loss of asthma control, which is called an asthma exacerbation, flare or attack.