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The chemicals in our body that spark a couple's romantic chemistry.

by Grace M. Leung


While we’d like to attribute love as the product of soul mates meeting, there’s a perfectly good scientific explanation for what we feel.

The phases of passion

Love has different stages, and how we feel during each stage is largely due to the hormones in our bodies.

In his article, “Hormones: Learning the Rules of Attraction” for British newspaper The Independent, Roger Dobson writes: “Hormones—from the Greek word hormo which means ‘to set in motion’ —are chemical messengers that travel around the body coordinating complex processes like growth and development, metabolism, fertility and almost everything the body does to stay alive.” And falling in love seems to fall under this definition as well.

Several websites, including and, cite the research of anthropologist Helen Fisher on this subject. Fisher, who works at the Rutgers University of New Jersey, says each stage of love is driven by different hormones and chemicals and describes the stages as follows:

Stage 1: Lust

This is the initial stage. The culprits: the sex hormones, testosterone and estrogen. Sex hormones push us to date and find partners.

Stage 2: Attraction

This is also known as the “lovestruck” phase—we can’t eat, can’t sleep. Our thoughts are filled with the one we love.

Sheila, 30, who met her present boyfriend while she was engaged to someone else, describes the onslaught of romantic feelings. “I knew I should avoid him, but at the same time the need to see him became even stronger.”

The culprits: chemicals known as neurotransmitters, which carry impulses from a nerve cell to another nerve, muscle, organ or tissue.

The main neurotransmitters involved in this stage are dopamine, norepinephrine, and serotonin—collectively known as monoamines. Dopamine triggers pleasure, and is associated with craving and desire. Fisher illustrates the link: “Couples often show signs of surging dopamine—increased energy, less need for sleep and food, focused attention and exquisite delight in smallest details of this novel relationship.”

Norepinephrine is what gives the body sudden energy in times of stress. In romantic situations, it has the more awkward effects of making you sweat, your heart race, and your mouth go dry.

Serotonin brings happiness and an overall sense of well-being; it regulates moods and exerts a calming effect. A study conducted by Donatella Marazziti, a professor of psychiatry at the University of Pisa in Italy, revealed that people with obsessive-compulsive disorder and those who had fallen in love within the past six months had serotonin levels 40 percent lower than those of normal subjects. Having the same chemical profile could explain why those in the attraction stage often obsess about the object of their love; like a drug, being with their special someone “heals” their unrest and brings their serotonin levels back to normal.

Stage 3: Attachment

This is when the bond grows into a longer lasting commitment, and partners feel a sense of calm, peace and stability. Two kinds of hormones come into play at this stage: oxytocin and vasopressin.

Oxytocin is released by men and women during orgasm, which helps explain why sex strengthens the bond between most couples. Kate Taylor, author of a book on relationships entitled Not Tonight Mr. Right, describes oxytocin bonding as becoming “literally addicted to the man who set it off…even his smell can jumpstart your heart rate and the brain chemicals responsible for your happiness, trust and intuition.”

Counselor Harriet Hormillosa of the Reintegration for Care and Wholeness Foundation says, “When there is an oxytocin bond, there is a sudden collapse of defenses or what we call the cathexis. We become vulnerable, and we allow the other person to get to know us more.”

Vasopressin is an anti-diuretic hormone that works with the kidneys to control thirst. It seems to be a significant factor for long-term commitment. When scientists suppressed the effect of vasopressin in the prairie vole, these monogamous animals changed their behavior—previously life-long mates lost their devotion to one another.

Fisher notes that high levels of oxytocin and vasopressin may interfere with dopamine and norepinephrine pathways, which may explain why attachment grows as passionate love wanes.

Kathryn and Phil, who have been married for 10 years, acknowledge how their feelings have evolved. “There are less of the kilig moments because we are used to being together,” says Kathryn. “No more blushing when teased, no more sweaty palms. But there’s still some kind of a swelling feeling when we are doing normal stuff or just being out together.”

Sniff and kiss

Finding a lifelong mate may require a little sniffing around, not just for pheromones—scent chemicals that are known to attract the opposite sex and initiate mating behavior in some animals—but a group of genes known as the major histocompatibility complex (MHC).

The MHC controls the immune system and influences tissue rejection, as in cases of organ transplants. In mating, it is more favorable to have a partner with a dissimilar MHC, as this will result in offspring that are more genetically diverse, and therefore more healthy and resilient.

Kissing is perhaps a “taste test” of MHC, and may explain why some people smooch, then conclude “there’s no spark” but can’t pinpoint why. It’s possibly a case of incompatible MHC, determined by chemical signals gathered from the exchange of saliva. This means that without you being aware of it, your brain may be getting and processing information, evaluating if the person you’re kissing is an ideal mate for you.

For more on chemical romance, get your copy of the Valentine issue of HealthToday magazine, out now in major newsstands and bookstores.

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