The phrase "running a fever when falling in love" is often used metaphorically to describe the intense emotional and physiological responses that people may experience when they are infatuated or deeply attracted to someone. It's not a literal fever in the medical sense, but rather an expression of the powerful emotions and physical sensations that can accompany the early stages of romantic love.
However, there is some scientific basis to the idea of "love sickness" and its effects on the body. When people are in love or infatuated, their brains undergo various chemical changes, including increased levels of neurotransmitters like dopamine, norepinephrine, and serotonin. These changes can lead to heightened feelings of pleasure, excitement, and euphoria, which are akin to the sensations associated with being "lovesick."
Additionally, falling in love and experiencing strong emotions can trigger the body's stress response, leading to increased heart rate, sweaty palms, and other physical symptoms similar to what one might experience during an actual fever or when under stress.
It's important to note that the intensity of these emotions and physiological responses can vary from person to person and may not be experienced in the same way by everyone. The feelings of being "lovesick" often subside or evolve into deeper emotional connections as a relationship progresses and becomes more stable.