Elasian tears

From Memory Alpha, the free Star Trek reference.

Elasian tears, secreted by Elasian females, contain a biochemical compound transmittable to Elasian (and Human) males. Upon skin contact, men became romantically infatuated and somewhat enthralled to the woman who infected them.

Men of Elas tried for centuries to dispel the tears' "mystical powers" without success. Troyian Ambassador Petri said of the phenomenon, "A man whose flesh is once touched by the tears of a woman of Elas has his heart enslaved forever."

In 2268, Captain James T. Kirk was infected by the tears of Elaan, the Dohlman of Elas. Although he was visibly affected and drawn to Elaan, he managed to overcome the tears' more compelling effects in a short time – just as Dr. Leonard McCoy believed a cure was within reach. First officer Spock speculated that the USS Enterprise was all the antidote Kirk needed for Elasian tears. (TOS: "Elaan of Troyius")