The sense of smell, or olfaction, is one of the most developed senses in a newborn baby. Infants are highly sensitive smellers, equipped to detect a wide range of chemical compounds in the air from the moment they are born. This heightened olfactory acuity means that a baby can indeed sense strong odors, including the volatile compounds found in flatulence or other intense smells, often with a sensitivity that rivals or even exceeds that of an adult. This powerful sense acts as a primary tool for navigating the world, distinguishing between sources of comfort and potential discomfort, and forming the earliest bonds necessary for survival.
How the Sense of Smell Develops
The biological foundation for a baby’s powerful sense of smell begins remarkably early, with the olfactory system developing well before birth. Olfactory receptors start to form in the nasal cavity around the eighth week of gestation. By the 24th week of pregnancy, these receptors are functional, allowing the fetus to begin sensing the chemical environment surrounding them.
Within the womb, the fetus is submerged in amniotic fluid, which acts as the baby’s first “scent classroom.” Odorous compounds from the mother’s diet, such as garlic or anise, are transferred into the fluid, giving the baby an initial exposure to a complex chemical array. This prenatal exposure creates a form of sensory memory, where the familiar scent of the amniotic fluid is later recognized as a comforting and safe cue after birth. The continuity of these scents—from the womb’s fluid to the mother’s skin and breast milk—is a crucial biological mechanism that aids in the transition to postnatal life.
Detecting and Reacting to Intense Scents
The ability of infants to detect intense smells stems from the fact that many strong odors, including those from human waste, are composed of volatile organic compounds (VOCs). These compounds, which often contain sulfur or ammonia, are detected by the baby’s highly sensitive olfactory receptors.
When an infant detects a noxious or intense odor, the reaction is often immediate and physical. Newborns are equipped with instinctive aversions to certain smells, particularly those associated with sour or bitter compounds that might signal toxicity or spoiled food. These aversions are observable as distinct facial expressions, such as grimacing or wrinkling the nose.
In addition to behavioral responses, strong odors can also trigger changes in the baby’s physiology. Studies have shown that exposure to irritating odors, even those from common hospital cleaning products, can co-stimulate both the olfactory system and the trigeminal nerve. The trigeminal nerve is responsible for sensing irritation, coolness, or pungency in the nasal passages, meaning an infant may not just “smell” the odor but also experience an irritating physical sensation. This combined sensory input can lead to changes in heart rate, breathing patterns, or movement as the baby attempts to process the intense stimulus.
The Critical Role of Scent in Early Life
Beyond reacting to unpleasant odors, the sense of smell is linked to a baby’s survival and emotional development. Olfaction is the primary tool newborns use to identify their caregiver, as they cannot yet recognize faces. Within hours of birth, a baby can differentiate the unique scent of their mother from that of a stranger.
Maternal scent acts as a powerful source of comfort and security. Exposure to this familiar scent has been shown to reduce crying and lead to less variation in physiological parameters, such as oxygen saturation, even during stressful procedures. This recognition helps to establish a secure attachment, which is essential for emotional well-being.
Scent also directly guides the baby toward nutrition. The aroma of breast milk attracts the newborn, stimulating their appetite and promoting latching behaviors. This olfactory guidance is so powerful that infants will preferentially orient toward a gauze pad carrying the scent of their own mother’s milk over that of another woman. The comforting and recognizable odors associated with the mother and feeding create a positive sensory feedback loop that supports the baby’s transition to extrauterine life.