As summer approaches, some notice lighter or longer hair, and nailnail more robust. These observations are not only sensations. Indeed, they are based on very real biological phenomena.
Research carried out in particular at the University of Bradford, in the United Kingdom, observed that the growth of beards reaches a peak in July, up to 60 % higher than that in winterwinter. Although these studies have mainly concerned men, the influence of saisonsaison seems to be also applied to women. In addition, various recent studies report a significant seasonal variation for nails, probably linked to better blood circulation at the ends.
Physiological mechanisms at work
Under the effect of heat, the blood vessels expand, promoting increased circulation to the scalpscalp and the ends. Result: a reinforced supply of oxygen and essential nutrientsessential nutrients to the synthesis of keratinkeratinthe proteinprotein structuring hair and nails.
More intense exposure to shelves UVUV In summer boosts vitamin D production by the organization. But this vitaminsvitamins plays a key role in the activity of folliclesfollicles People and participates in keratin production, essential for the health of hair and nails.
A seasonal rhythm in hair
The hair follows a cycle in three phases: growth (anagène), transition (catagen), then rest (telogen). At the end of the summer, increased number of hair passed into a telogen phase, which leads to a more marked fall in autumnautumn. A normal and temporary phenomenon. This increase in the fall is often perceived as linked to summer, but it is actually the result of the cycle shifted by the season.
Furthermore, according to the dermatologistdermatologist Robyn Gmyrek, « Heat causes a general increase in blood flow, which improves traffic. This, in turn, increases the amount of nutrients and Growth factorsGrowth factors Bring to the hair follicle ».
A small downside however. The available data show that hair growth speed can increase up to 60 % between its minimum and maximum value. It should also be remembered that basic growth remains less than half a million per day. In other words, even if your hair grows a little faster in summer, the difference remains difficult to perceptible to theeyeeye not.
So, if you feel like they are growing much more, it may be due to a side effect of the season. “” I think that given that people wear less clothes and that many women shave the exposed parts of the body, they are particularly sensitive to the slightest outgrowth. Even a millimeter or two “Specifies the dermatologist.
And the nails, then?
Several factors influence nail growth speed. Some fingers grow faster than others. The middle finger and the annular, for example, often exceed the ear or the thumb. The dominant hand also sees its nails grow a little faster, due to increased muscle activity. And when a finger is injured or sick, growth can clearly slow down or even stop.
Nail growth is less documented than that of hair, but several sources report a slight acceleration in summer compared to winter, probably under the effect of temperature and blood circulation. However, the effect remains discreet, often in the order of millimeters per month, barely perceptible on a daily basis.
In 1941, American doctor William Bean embarked on a self-study. Each month, for more than 40 years, he scratched a line at the base of his nails and measured their progress. Despite the accuracy of his method, he never noted seasonal variation. No accelerated growth in summer, nor slowdown in winter, despite solid evidence in favor of such an effect? The reason? He suspected that our modern way of life between central heatingcentral heating et air conditioningair conditioninghad disconnected from natural thermal variability.
In short, a bit like with your hair, if your nails seem longer in summer, it may be true, or maybe you are simply more attentive to these details when your hands are in the open air.
So, a simple optical or real summer push illusion? If science confirms a slight acceleration of hair and nails growth during the summer, our perception is also influenced by our habits, our environment and what we choose to observe. It remains to be seen whether, in the future, our always more interior lifestyles will eventually smooth these seasonal effects, or if it will be a ray of sunshine to revive, discreetly, the machine.
