Researchers have mapped the chemical changes that occur in a person's brain when he falls in love and discovered the areas that activate and shut down during the heady days of courtship.
Scanning technology allows neurologists to unravel the mystery of why love can turn us giddy, irrational and even ridiculous and make us nervous and unstable.
Researchers hope it may also one day reveal why a few of us might overstep the mark when dealing with the object of our affections, the 'Daily Mail' reported.
They found the frontal cortex, vital to judgement, shuts down when we fall in love. MRI scans show this de-activation occurs only when someone is shown a photo of the person they adore, causing them to suspend all criticism or doubt.
"When you look at someone you are passionate about, some areas of the brain become active. But a large part is de-activated, the part that plays a role in judgement," Semir Zeki, professor of neuro-aesthetics at University College London, said.
Zeki believes the brain may behave in this way for "higher biological purposes" - it makes reproduction more likely. If judgement is suspended, the most unlikely pair can get together and reproduce.
Studies have shown brain chemical dopamine is at higher levels in those in love, the report said.
Dopamine is key to our experiences of pleasure and pain, linked to desire, addiction, euphoria, and a surge may cause such acute feelings of reward that it makes love hard to give up.
Tests show that taking opioid drugs such as cocaine have a similar effect on dopamine as love.
A side effect of rising dopamine levels is a reduction in another chemical, serotonin, a key hormone in our moods and appetite.
Serotonin levels may fall in a similar way to those seen in people with obsessive-compulsive disorder, explaining why love can make us feel anxious and jittery.
According to researchers, the love chemical we are most familiar with is adrenaline. This hormone is behind why our heart races, palms sweat and mouth goes dry when we see the person we like.
The same hormone is also released when we are frightened. This means that two people only vaguely attracted to one another can fall madly in love if they go through an exciting or scary experience together.
Researchers said it may also explain the lure of forbidden love.