GROW YOUR OWN MEDICINE  Lemon balm - Melissa officinalis  The cold-sore treatment  This member of the mint family has antiviral properties and can help treat cold sores. Pick 2 to 3 teaspoons of leaves, pour 1 cup boiling water over top, and let steep for 10 to 15 minutes. Dab a cotton ball in the warm tea and apply to the cold sore daily.