It is one of the most natural practices in the world. Every time we want to spray ourselves with perfume we do it automatically on wrists, on the neck and behind the ears. But who decided this? They are not (completely) random areas of the body, because they are the so-called “impulse points“, that is, the places where the arteries run closest to the epidermis. It is no coincidence that to feel the heartbeat, you feel your pulse. Well, there is a theory that wearing perfume on these points should help it spread more more because these areas are warmer compared to the rest of the body. But is it really true? Spoilers: no, there is no scientific evidence to confirm thisbut it’s mostly a question of practicality.
Perfume is applied in some places for convenience
According to the theory of “pulse points” we should place the perfume in areas where arteries flow particularly close to the surface of the skin, such as the radial one in the wrist, the brachial one in the internal fossa of the elbow, the carotid one in the neck, or even other more strange ones like the popliteal artery behind the knee or the posterior tibial artery located in the ankle area.
According to the pulse point theory, these areas heat the skin because the blood vessels are closer to the epidermis and the heat provoked would help the scent to spread. Actually, it’s not really like that.
Various tests have been done on regional skin surface temperatureto understand which parts of the skin are the warmest. A study conducted in 2019 measured temperatures in 15 body regions, including the neck and forearm, in 30 participants. The areas with the highest temperature were actually recorded in the neck area, on the forehead, on the palm of the hand, but also the perilabial and nasal area where perfume is usually not placed! The test also has limitations: one of them is that the participants maintained a supine position, they were not moving and this may have distorted the measured data.
Furthermore, we must consider that some of these places are less accessible and practical for both the wearer and the smeller. In short, it rarely happens that someone smells our knees! Finally, some of these areas are often covered by clothing, so it would be inconvenient to put perfume in these areas. We can therefore say that the main reason why perfume is put on the back of the neck and on the wrists is first of all practicality.
Thermoregulation can affect scent diffusion
More than pulse points, thermoregulation can actually help the diffusion of scent. Temperature control also depends on the reactions of the hypothalamus due to the external environment. For example, if the body feels cold it sends a signal to the nervous system which activates the systems thermoregulation, to warm us up in reaction to the change in temperature of the external environment.
The increase in temperature increases the rate of evaporation of volatile aromatic molecules present in the perfume. These molecules are in fact the ones that evaporate easily reaching our nose and are responsible for the smell of the perfume we perceive. And since the persistence of an olfactory compound depends on its evaporation rate, the skin temperature will affect the diffusion of the molecules.
Then the perfume it may spread better to areas where we sweat (where the sweat glands are present) in which the temperature increases more favoring the evaporation of the aromatic molecules. The problem is that the evaporation of sweat helps to cool the skin, making us find ourselves in the opposite circumstance, with a lower body temperature.
So, to conclude, there is no scientific evidence to support the pulse point hypothesis, and although thermoregulation could play a role in the diffusion of volatile molecules present in the formulation, the perfume is worn on the wrists and behind the ears mainly for convenience and convention.
Does the perfume last longer on fabrics?
The answer is: it depends. The fibers of the fabric allow the perfume molecules to remain trapped inside them and this effect can last for more or less time, depending on the type of fabric.
In a study published in‘Industrial Textilia Journal, Through the use of some sensors, scientists have tried to measure how long a perfume remains on clothes. According to the study data, fabrics with higher content of cotton they retain the fragrance more thanks to their hydrophilicity and properties of absorbing water. At the same time however the fabrics more intertwined (like twill, with a diagonal weave) are more porous and retain perfume molecules better than yarns woven with other wefts.
Finally, the permanence of the fragrance increases as the density of the fabric increases or the number of threads decreases. This has to do with ownership of perspiration of the tissue which, when it decreases, slows down the diffusion of the perfume.
