At my first symptom of a cold, (Sore throat) I swab my nostril with tee tree oil. Same with other things. I used it before being required to test for covid for medical reasons. I will never be without it in my med cab. It's anti bacterial and microbial. You may want to dilute it with water before swabbing. I burns a little. I wet the Qtip with water then dip the end into the oil. I've taken it internally when fighting an infection, just a drop in water and drink it or put a drop under my tongue.