The crushed leaves, when rubbed on the skin, are used as a repellant for mosquitos.
Lemon Balm is also used medicinally as a herbal tea, or in extract form. It is claimed to have antibacterial, antiviral properties (it is effective against herpes simplex), and it is also used as a mild sedative or calming agent. At least one study has found it to be effective at reducing stress, although the study's authors call for further research. Its antibacterial properties have also been demonstrated scientifically, although they are markedly weaker than those from a number of other plants studied. The extract of Lemon balm was also found to have exceptionally high antioxidant activity.
Lemon balm is mentioned in the scientific journal Endocrinology where it is explained that Melissa officinalis exhibits antithyrotropic activity, inhibiting TSH from attaching to TSH receptors, hence making it of possible use in the treatment of Graves' disease or hyperthyroidism. 
Lemon balm essential oil is very popular in aromatherapy. The essential oil is commonly co-distilled with lemon oil, citronella oil, or other oils.
Lemon balm is used in some variations of the Colgate Herbal toothpaste for its soothing and aromatic properties.