There is always a chance that the person's thickened phlegm could get worse rather than get better over time, which can be brought on by some irritants. It is strongly advised that people take all reasonable steps to keep irritants in the air to a minimum in order to make the other remedies on this list effective at permanently eliminating phlegm. While healing from the infection or underlying disease generating the phlegm, people should avoid pollution, chemicals, and intense scents as these are the main irritants.

These irritants can aggravate the phlegm by causing problems in the airways, nose, and throat. These compounds can irritate someone's nose or throat, which causes their body to respond by generating more mucus. While it may not always be able to completely avoid airborne irritants, staying indoors while ill should help people reduce their exposure to these irritants.