Body odor tends to freak people out. We are led to believe we should douse ourselves in fragrance—from scented lotions and deodorant to perfumes, cologne and eau de toilette. (Do you even know the difference between the latter three?) But the reasons why our bodies produce odors and why we can smell are tied to our DNA and to our survival as a species. Olfaction, the act or process of smelling, is part of the chemosensory system, alongside gustation (taste) (1). Human odors serve as a means of social communication, primarily in parent-child and sexual relationships. Scent also varies throughout the cycle and pregnancy (2–4).
Let’s reevaluate B.O. Smelling from birth Producing and picking up on odor may be an important tool as early as just after birth. One study showed mothers were able to distinguish the scent of their offspring’s clothes from other infants’ garments within a week of giving birth (2). Another study found breastfed infants were able to differentiate their mother’s scent amid odors from unfamiliar females within two weeks of being born (3). It’s also been found that individuals have unique olfactory signatures that serve as a means of recognition for kin, so you can sniff out your close ones. Pheromones? You’ve probably heard of these mysterious substances called pheromones that induce obsession and love.
Prince, a pioneer in sexy music, has an entire song about the supposedly potent chemicals: “Pheromone, controlling my every motion/ Pheromone, when your body’s wet.” Pheromones are chemical substances that are usually produced by an animal and serve as a stimulus to other individuals of the same species for one or more behavioral responses (5). Pheromones are a captivating topic, yet tricky to study, so we’re still left a bit uncertain of how exactly they function in people (and, perhaps, if they exist at all). That being said, there does seem to be a different effect of pheromones in humans compared to other mammals. Human pheromones are found in secretions, like sweat, and perceived through the nasal septum; they possibly modify mood state, rather than stimulate the stereotypical “spellbinding” physical responses we are known to associate with pheromones in animals (4, 6).
That suggests carnal reactions from pheromones occur in non-human mammals. Sorry Prince. Just how data hasn’t found proof of cycle syncing, it’s unlikely that smelling other people’s body odor will alter your hormones enough to affect your cycle (6). However, it’s clear there is a correlation between odor, smell and appeal—the involvement of pheromones here is an open question. Scent throughout the cycle Since it’s only during the fertile window that conception can occur, it’s been found that males may be subliminally capable of distinguishing when ovulation occurs from components in female scents (4).
“You smell great! What’s that you’re wearing?” “Oh, this? It’s just my fertile fragrance.”
In one study, body odors of females were collected from secretions and various parts of their bodies, at various times throughout their menstrual cycles. These odors were then ranked by the subjects’ male partners. Body odors were found to be perceived as most pleasant smelling, and as longer-lasting, during their ovulatory phase (4). Another study tested the attractiveness of t-shirts’ scents worn by pill users and people not using hormonal contraception. The t-shirts of people not using hormonal contraception were ranked the nicest smelling, by both males and females, during their ovulatory phase (7). There was no trend for pill users, which was clarified by stating, “oral contraceptives do not make odors unattractive, but only demolish the cyclicity of attractiveness of odors.” (4) Some t-shirt studies have been criticized.
Several components in odor in the ovulatory phase, including steroid hormones from apocrine sweat glands, signal peak fertility and are favored regardless of reproductive intention—which doesn’t mean you smell worse because you’re on the pill or because you’re in the luteal phase. There’s also curiosity about changes in female smelling sensitivity across the cycle, and research has found conflicting results. Some studies claimed greater smelling abilities occur around the period, while other results claimed peak smelling abilities occur around ovulation (8–9).
One study found no significant variance across the cycle (11). These inconclusive outcomes leave us unclear about how the nose in tune with cycle. We do know olfactory cues have subtle ways of indicating fertility and familial identification. Parent-child bonding begins with scent and smelling. With the cycle, body odor attractiveness peaks around the time an egg is released. Does your sense of smell change across your cycle? Do you notice different behavior from yourself and/or a partner during your ovulatory phase?