Is It Possible To Have An Involuntary Reaction To Someone You Find Attractive?

Yes, it is very possible.

THE ATTACHMENT SYSTEM (termed “companionate love” in humans) is characterized in birds and mammals by behavior that may include defense of a mutual territory, mutual nest building, mutual feeding and grooming, separation anxiety, and shared parental chores.

In humans, attachment is also characterized by feelings of calm, security, social comfort, and emotional union. Attachment is associated in the brain primarily with the neuropeptides oxytocin and vasopressin. This emotion system evolved to motivate individuals to sustain their affiliations long enough to complete the impulse feeling of attraction towards their own species of the opposite sex.

For each system, the neural circuits can be expected to vary from one species to the next, among individuals within a species, and over the life of an individual. The three emotion systems also act in concert with one another and with other bodily systems.

For example, a person may begin a sexual liaison merely for sexual pleasure, then become romantically involved with this sexual partner. He can become deeply attached to this partner, too, and these enhanced feelings of attachment can be explained biologically.

Being in love triggers a cocktail of chemicals in the brain. Some of the hormones — which also act as neurotransmitters — that the body releases when we’re infatuated can have a soothing effect. These are the chemicals that cause the involuntary impulses that make one feel attracted to the other.

Also: https://uiz.io/TAsS