Sex Pheromones: What Are These Chemical Messengers?

Medically Reviewed by Zilpah Sheikh, MD on November 02, 2023
5 min read

Pheromones are chemicals that animals and humans use to communicate. Our bodies release pheromones through sweat, urine, semen, breast milk, and vaginal fluid.

The theory is that these substances cause a reaction in the people around us. For example, pheromones might help us attract a mate. They're sometimes called “love chemicals” for this effect. But while there is a direct link between pheromones and mating in the animal world, the effects and even the existence of these chemicals in humans have been hotly debated.

The original concept of pheromones came from studies of insects in the 1930s. Researchers used the term “ectohormone” to describe the hormones that insects release outside of their bodies. By the late 1950s, scientists had renamed the substances released by members of the same species as pheromones.

Pheromones aren't the same as hormones, though the names sound similar. Hormones are chemical messengers such as estrogen, cortisol, and testosterone. They work inside our bodies to control things such as growth, mood, and sexual function.

Pheromones work outside the body. They act like signals to members of the same species. Animals release pheromones to mark their territory, find prey, attract a mate, or recognize other members of the same species.

These chemicals affect not just sexual attraction but other behaviors such as:

  • Mood
  • Parent-child bonding
  • Social connection
  • Thinking

Pheromones come in four main types:

  • Releaser pheromones work right away and elicit a specific response from the other person.
  • Signaler pheromones give information about the person who releases them. For example, they help a mother tell her own baby apart from other babies.
  • Modulator pheromones affect mood and emotions. 
  • Primer pheromones affect hormones, for example during pregnancy or menstrual cycles.

Mammals detect pheromones through the olfactory system deep inside their nose. This is the same system that helps us smell and taste food.

Chemical signals reach a mammal's nose as a gas or liquid. Organs inside the nose -- the vomeronasal organ (VNO) and main olfactory epithelium (MOE) -- detect pheromones. Jacobson's organ is another name for the VNO. The VNO and MOE then send signals to the animal's brain to process.

It's not clear how the process works in humans. We do have VNO organs, but they're small and may be too poorly developed to process pheromones like the VNO organs in animals can. More likely, we process these signals through our olfactory system.

Experts don't even agree on whether humans produce pheromones. Some scientists say we don't make them. Others say human pheromones do exist, but they haven't been identified.

Menstrual synchronization

There's been a lot of theories about pheromones and women's menstrual cycles. Women who live together in college or who have sisters might have noticed that their periods sync up.

The idea stems from a 1971 study that claimed pheromones change the cycles of women who live together. The phenomenon became known as the McClintock effect after the student who conducted the study.

Since then, other studies have debunked the idea that living close to other women makes periods align. The authors of these new studies say the synced-up periods found in the 1971 study happened just by chance.

Fertility and depression

Although there's still a lot we don't know about pheromones, research is looking into how we might use them as fertility treatments for couples who want to conceive. For example, one study found that exposure to male pheromones slowed aging in female roundworms' eggs. Findings like these in animals might pave the way for new infertility treatments in humans.

Couples who are having sexual problems might one day use pheromones to enhance desire. There's evidence that substances in men's sweat improve women's mood and focus. And women who are more focused and happier have a better sexual response and more satisfaction. It's also possible that pheromones could be used as a mood enhancer to relieve depression.

Subtle but strong influence

If you're looking for the partner of your dreams, pheromones in your body scent might play a role in attracting a mate. Pheromones might make you more attractive to a possible partner and vice versa.

How another person perceives our body odors as pleasant and sexy is a highly selective process. We usually smell best to a person whose genetically based immunity to disease differs most from our own. This could be a benefit in the long run, making for stronger, healthier children.

Pheromone perfumes

Not surprisingly, some companies have taken advantage of the role that scent plays in attraction. They use pheromones to sell products designed to help us find love (or just sex). Pheromone-infused perfumes claim they can “boost attractiveness” and grab the attention of the object of your affection.

The idea might sound appealing, but there's no evidence these products work. When these perfumes were tested out in studies, not only did they not increase attractiveness, but also they had the opposite effect.

Pheromone collars, sprays, and other products for calming anxious pets have more evidence to back them up. A pheromone collar reduced anxiety in dogs that were exposed to a simulated thunderstorm. And dogs staying at a veterinary hospital who were exposed to pheromones had less separation anxiety than untreated animals.

Pheromones help animals with various activities, ranging from finding prey to attracting a mate. In humans, there's a lot more debate about what pheromones do, or even if they really exist. Until we know more, there isn't much point in buying pheromone products because there's no evidence they work.

What is the role of pheromones in love?

Pheromones are sometimes called “love chemicals” because they help animals and insects attract a mate. Experts are divided on whether pheromones have the same effect in humans, or if they even exist. Some small studies suggest that pheromones do boost sexual responses in men and women, but we need more evidence to confirm this effect.

What do your pheromones smell like?

Whether we can even smell pheromones is a matter of debate in the scientific world. And if we can detect these chemicals, what they smell like depends on who is smelling them. In studies of pheromones, people described the scent as “musky,” like sweat or worn clothes.

Do human females release pheromones?

Researchers have found a pheromone called estratetraenol that women release. They first discovered it in the urine of pregnant women, but it is likely also present in sweat and other body fluids.