Some scientific researches say that it happens due to lack of oxygen in the body. While some studies show that it is a reflex action used by the body to cool off the temperature of the brain. Then, some studies proclaim that there are some "mirror neurons" in the brain, due to the presence of which, when we see another person yawn, we tend to yawn, too!
Some say that yawning was a kind of non-verbal communication used by people in olden times, to convey that they wanted to change the activities that are going on! Just like too many causes, there are innumerable ways to stop a yawn, too. Read about a few of them here, and try them the next time you want to stop yourself from yawning.
Do not eat a heavy meal, especially for lunch in the afternoons. When the body tries to digest a heavy meal, it often makes a person feel tired, resulting in excessive yawning.
Whenever you feel the urge to yawn, take a sip. This will suppress the yawn, and at the same time, hydrate your body, reducing any kind of tiredness that is a result of lack of water.
Get Some Fresh Air
Some researches show that a person tends to yawn in excess when his brain is overheated. Yawning is a mechanism employed by the body to cool the brain off.
In most cases, yawning is harmless. However, sometimes, excessive yawning can be caused by health conditions and diseases such as brain tumor, epilepsy, heart disease, multiple sclerosis, sleep apnea, amongst others. So, if the excessive yawning continues even after taking all these measures, consult a doctor for proper diagnoses.