As a medication, lysine is used probably most commonly in the treatment of herpes simplex labialis, better known simply as herpes or cold sores. It works best as a preventative option, although it can reduce how long an outbreak lasts.
Anisocoria is a condition in which the two pupils of the eye are different sizes; in other words one pupil is larger than the other. In some cases, the abnormal pupil may be the one that is smaller and in other cases the abnormal pupil may be the one that is larger.
And to be honest if you're trying to look closely enough at his eyes to see if his pupils have dilated or not it can be a little weird XD However it's true that the pupils dilate when the person finds someone they are looking at attractive.