The Chemistry of Love

I was sitting in the lobby of my accountant’s office, flipping absentmindedly through a magazine when she walked in. I’ve never had a visceral reaction as when I saw her walk through that door. There was just something about her; I felt head over heels… My heart started racing and I had butterflies in my stomach…

This is the amazing time when you are truly love-struck. With an irresistible cocktail of chemicals, our brain entices us to fall in love. But is it really us or is it yet another nature’s trick to keep our species alive?

Scientists agree that there are three stages and processes in love:

Stage 1 – Attraction: Dopamine and Adrenaline

When you fall in love, your brain starts sending signals before you can even blink. Your heart races and palms sweat: adrenaline is getting released from neurons. Then, when you are close to your sweetheart, dopamine is released, which triggers euphoria and feelings of bliss, increased energy, increased energy, less need for sleep or food,  and focused attention on your new relationship. Phenylethylamine (PEA) is the chemical responsible for releasing adrenaline and dopamine. Biologically speaking, with the combination of dopamine, adrenaline, and PEA in your body, you’re experiencing something similar to a cocaine high. And it doesn’t matter whether you just met this *special* person or you ‘ve known them for ages; these love signals can be released at any time. Actually, no, not at any time. Only when mother nature thinks the timing is right** (see below).

Stage 2 – Lust: Testosterone kicks in


That is about the time that androgens and estrogens kick in. Estrogens and androgens are steroids, which are the female and male sex hormones, respectively. Testosterone is the sex hormone in both male and females, which is what gives us libido and sex drive. This hormone is elevated when we are in love. This makes sense as you’re most concerned about sex when it’s most likely to result in reproduction. Some people argue that this Stage precedes Stage 1, but it’s up to you to decide 🙂

Stage 3 – Attachment: Oxytocin, the love hormone

In the long run, two other hormones make their headway when emotionally involved: the “hormones of attachment”, oxytocin and vasopressin.

Oxytocin. Notice something? As we go down the love chain, the molecules appear more complex; sort of like love-life!

Oxytocin is a hormone stored in the brain. When the hormone is released in the brain, it results in feelings of attachment and bonding. It has been found that oxytocin gets released at orgasm, which is why couples feel much closer to one another after they have had sex. Oxytocin is also released at childbirth and is partly responsible for the strong bond between mum and baby (actually oxytocin has a Greek root: “οξυτοκίνη”, which means “quick birth”). So, if you feel the urge for a stay-at-home movie night to cuddle with your beau, it may be oxytocin at work.

Vasopressin is another important hormone when it comes to relationships.  Scientists studied the prairie vole, which is known to be monogamous and to express vasopressin like humans. When the researchers introduced vasopressin receptors to the “meadow vole”, the promiscuous cousin of the prairie vole, these playboys reformed their ways and fixated on one female, choosing to mate with only her – even when other females tried to tempt them!!

Wondering why some people find it hard to get emotionally involved or committed?

Some people might be less prone to form stable relationships because they might be not express as many “oxytocin or vasopressin receptors” (proteins that take up oxytocin or vasopressin) in their brains. Thus, some people are not that sensitive to the “commitment hormones” oxytocin and vasopressin. Experiments in animals showed that if you remove the oxytocin or vasopressin receptors, these animals cannot form strong bonds with each other any more.

**When do we fall in love?

Timing is important. The perfect partner can sit right next to you at a party, and you might not notice him or her if you’re too busy at work, enmeshed in another relationship, or otherwise preoccupied. But if you’ve just moved to a new city, recovered from an unsatisfying love affair, begun to make enough money to raise a family, are suffering through a difficult experience, or have a good deal of spare time, you are ripe to fall in love.

So love appears to all be yet another one of nature’s traits:

Romantic love evolved to enable you to focus your energy on just one person at a time, conserving time and energy. The sex drive evolved to get you out there looking for partners. Attachment, the feeling of security you can feel with a long-term partner, evolved to help you stay together long enough to raise kids.

Posted on February 14, 2012, in chemistry and everyday life, love, science of life and tagged , , , , . Bookmark the permalink. 6 Comments.

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  2. Hi there,
    I really like your article and I am interested in learning about the role of Vasopressin in the feeling of falling in love or in a relationship. And I have a question and can not clear it myself, hoping you can help clarify it:
    In you post it said “Essentially, vasopressin released after intercourse is significant in that it creates a desire in the male to stay with his mate…” and I also heard from Dr. Dawn Maslar (2016) that “Vasopressin goes up when a man is stimulated and the Vasopressin drops when he had sex”.
    My question is: is there a logically explanation about this cause I think both sound about right? and if there is a way to explain about this with regard to the level (high or low) or to the stage of relationship that causes the difference?
    Your kind response will be much appreciated. I can be reach at or 216-235-0237.
    Tuan Le

  3. Learn alot now, I want to learn more on this topic.

  4. So sweet,,🥰🥰

  1. Pingback: A Day in the Life of a Computational Chemist | Life is Chemistry

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