Asthma is a condition of the lungs where the windpipes called airways, that transmit the air back and forth into the lungs during breathing are narrowed. This narrowing disables a person from moving air in and out of his lungs freely which leads to the sensation of difficulty in breathing or chest tightness.
Why some people have asthma and others do not is that in some people the windpipes are over sensitive to environmental substances causing their narrowing and in some they are not.
Now one feature of this narrowing of windpipes in asthma is that it is not present always. Instead, it comes and goes depending on the exposure to a potential trigger. When a patient is exposed to a trigger (cold air, pollen, dust, flu etc.), the windpipes will get narrowed, and when the patient is treated with medications, the windpipes get wider again.
The episode of narrowing and difficulty in breathing as a result is called an attack of asthma. Often during an attack or uncontrolled asthma, together with narrowing of the windpipes, there is also excessive production of the phlegm.
Hence if you are experiencing bouts of chest tightness, or episodic shortness of breath with some days with no difficulty and some days with difficulty breathing or chest tightness, you may be having asthma.
Now while blowing through a hollow tube does not produce any sound, where as blowing into a flute or a whistle does, same when air flows through the normal windpipes it does not produce any sound, whereas when it passes through the narrowed airway it produces a whistling sound which is called wheezing.
Hence if you are experiencing wheezing, you may be having asthma. It is more likely to have asthma if your parents or siblings have it. Hence if you have a family history of asthma, then your symptoms as stated above may be due to asthma.
Since asthma is a genetic disease, people are born with it. This means that people can start having symptoms in childhood. This, in no way means, that such people will suffer throughout their lives because of asthma.
In some patients symptoms are more frequent and severe, whereas some may only experience mild symptoms that too occasionally. Even those with severe symptoms when treated with currently available medications can remain symptom free most of their lives.
Hence if you have been having difficulty in breathing, chest tightness, or wheezing since childhood, you are likely to have asthma than any other disease. Lastly, asthma not just causes difficulty breathing, chest tightness, or wheezing, but also chronic cough. Hence, if you are experiencing chronic cough, you may be having asthma.
In summary, asthma starts in childhood, and causes difficulty breathing, chest tightness, wheezing, and chronic cough in an episodic manner with good days and bad days. It runs in families and hence having parents or siblings with asthma is a clue that your symptoms may be from it.