What Are Pheromones? A Closer Look At The Science & Research

"Pheromones are hormone-like chemical messengers that send information outside of the body," family medicine specialist Pouya Shafipour, M.D., explains to mbg. "[Whereas] 'typical' hormones travel in the bloodstream and serve to communicate between other cells in the body [only], pheromones send messages that affect other animals of the same species."

Pheromones are famously thought to increase sexual desire, among other subliminal effects on human behavior, says psychologist Dana McNeil, PsyD, LMFT. They "act as an agent of change," encouraging certain behaviors, she explains, though those may include survival-related behaviors like sensing predators, locating nearby food, or engaging in other protective mannerisms, in addition to potentially influencing the desire to seek out intimacy and sexual activity.

Pheromones are thought to be externally secreted2 through urine, semen, vaginal secretions, breast milk, axillary sweat, and potentially saliva and breath. Once released into the air by one individual, these secretions can then theoretically be detected by another individual via receptors in their nasal passages, explains Shannon Chavez, PsyD, a licensed psychologist and sex therapist for personal lubricant brand K-Y. 

Some animals have a well-developed vomeronasal organ located in the nasal septum. That organ is what's thought to detect pheromones secreted from other animals in proximity, according to naturopathic physician Jolene Brighten, N.D. Although pheromones are recognized through the nose, Chavez notes they may not have a detectable scent. 

When a pheromone is detected by the recipient, it's believed to send a signal to the brain that can influence mood, reproduction, sexual functioning, and more. The body essentially uses this information to make sense of its environment and respond appropriately: "Pheromones play a role in the survival and evolution of the body," Chavez explains. "They trigger puberty, changes in reproductive function, and survival instincts that may be necessary for social environments where there is a threat."

There's a lack of scientific consensus as to whether human pheromones exist at all. Despite a body of research3 supporting the theory, many scientists question the validity of those results based on the way the studies were conducted.

For instance, an often-cited 1971 study led by psychologist Martha McClintock4 infamously once posited that pheromones could sync up women's menstrual cycles if they lived in proximity together. The news quickly spread and became common knowledge before the findings were repeatedly debunked over the years5 with additional researchers unable to repeat McClintock's results. 

Scientists have studied pheromones for years but haven't been able to scientifically validate6 their correlation to sexual attraction due to the complexity of human interaction, the genetic variability of odors, and the molecules themselves; the components of pheromones are notoriously tricky to isolate3 and empirically test in well-controlled, peer-reviewed settings. 

"What makes it really difficult is that research seeks to isolate scents alone to detect a response," Brighten adds, "when in reality, it's likely several variables that cause someone's behavior to shift when they take [chemicals] in."

She also points out that not all humans have that vomeronasal organ7, and even if they do have it, it’s been found to be a nonoperational organ in humans, so it wouldn't be able to detect pheromones anyway. Meanwhile, other research has found some of the most commonly cited human sex pheromones as having no effect on attractiveness or gender perceptions.

The theory behind the link between pheromones and sexual attraction revolves around the potential pheromones androstadienone, which men produce and are thought to sexually appeal to women9, and androstenone, which is thought to signal dominance or aggressiveness10. 

According to McNeil, men also secrete a greater amount of a potential pheromone known as androstanol, which is thought to be present in sweat and may activate a portion of the hypothalamus. In a study of 16 heterosexual women, PET scans revealed smelling androstenol triggered specific networks in the brain involved in human reproduction and may be involved with menstrual synchrony. 

Women also secrete the potential pheromones copulin and estratetraenol, which reach a peak during their ovulation cycle, McNeil explains. As reported in a study in the scientific journal Evolutionary Psychology11, "sensing" a woman's fertility this way may spike men's testosterone and subsequently increase competitive behaviors like dominance and guarding. It's also been theorized that women's tears contain a chemosignal12 that reduces male aggression.

While decades of research haven't been able to definitively prove the roles pheromones play in human attraction, it is apparent your sense of smell does matter in mate selection, so it shouldn't be overlooked, according to Rebecca Alvarez Story, M.A., sexologist and co-founder of Bloomi. "From a biological perspective, [smell] is an arousal system and contributes to sexual attraction, stimulation, and satisfaction," she says. "If an individual wants to be sexually appealing, the most direct approach is to practice good hygiene, eliminate any repulsive odors, and use alluring fragrances." 

Evolutionarily speaking, it may be wise to intuitively trust what your smell is telling you since it's one of the oldest senses used for survival and for environmental interaction. A small study of 70 people13 indicated odor sensitivity positively correlated to sexual experience, with women reporting a higher frequency of orgasm during intercourse. Another notable study in the Journal of Personality and Social Psychology14 randomly assigned 96 women to sniff out different scents (a neutral smell, their partner's smell, a stranger's smell) and reported the smell of a romantic partner lowered stress while the smell of a stranger increased stress levels. It suggests smell plays a critical role in social communication but calls for further studies.

Meanwhile, in a 2021 study15, anecdotal reports found women are less attracted to their partner's body odor during the dissolution of a relationship. "I have found that couples on the brink of divorce will no longer find each other's scent appealing and notice new scents in their partner that are not pleasurable, such as noticing their breath or sweat as foul," Chavez adds. 

Pheromones are still being studied, and there'll be more information to come about whether they exist in humans, their exact function, and how humans may respond to them. While the exact relationship between pheromones and their ability to act as an attractant is ongoing, the part you can control is understanding arousal.

"What is often left out of these conversations is how arousal works," Brighten notes. "Not all women become spontaneously aroused, and instead they need much more than what they perceive as a hot body or good smell to get them in the mood. Companies have tried to make pheromones, but it's based on the premise that all [they] have to do is smell you and it's on."