Health experts say that the phlegm, especially of a disease-carrier, can spread air-borne respiratory diseases. According to the World Health Organisation’s (WHO) official website, “Tuberculosis (TB) is spread from person to person through the air. When people with lung TB cough, sneeze or spit, they propel the TB germs into the air. A person needs to inhale only a few of these germs to become infected.”

When a person spits in a public area, it may not have immediate affects on people around. However, someone steps on the saliva, will then carry the germs with him or her. When the person removes his or her shoes, the germs can easily be transferred. Additionally, if the person uses public transport and put his or her feet on a seat, the person to use the seat next can also become a carrier. It is a vicious cycle.

There are several other illnesses that people can be exposed to with direct contact with a carrier’s saliva. The WHO states that people can be exposed to the even Ebola virus from direct physical contact with body fluids like blood, saliva, stool, urine or sweat of an infected person and soiled linen used by a patient.

Additionally, the virus which causes smallpox is contagious and spreads through person-to-person contact and saliva droplets in an infected person’s breath.

According to a report published by The Guardian, a daily newspaper in the UK, there are some health risks associated with chewing gum. The action of chewing stimulates the cells lining the stomach wall to produce digestive acid. When a person chews gum, this mechanism comes into effect, but there is no food being swallowed to be digested.