Summer often evokes health, vitamin D, relaxation. However, it is also a period when some of us see their organization flank. Rhumes, digestive disorders, allergies, fatigue blows … These ailments that seem contradictory to the image of the hot season are actually a reflection of a fragile balance that the body sometimes struggles to maintain.
The heat: an enemy who exhausts the body
Thermal stress and weakened immune system
When temperatures regularly exceed 30 ° C, the body must redouble their efforts to maintain its internal temperature around 37 ° C. For this, it activates sweating, natural evaporation mechanism to cool the skin. But this intense sweating can cause even slight dehydration. Already at 2 % body water loss, immune performance clearly decreases, according to the National Institute for Research and Security (INRS).
This dehydration aggravates the viscosity of the blood and slows down circulation, which complicates the transport of immune cells to areas of infection or inflammation. As a result, the immune system becomes less effective, and viruses or bacteria have a boulevard to settle.
Exhaustion due to heat: an underestimated risk
At work, whether outdoors or indoors, the heat requires additional fatigue. The European Agency for Occupational Safety and Health recalls that physical work in high heat increases the risk of exhaustion, which weakens resistance to infections. Headache, nausea, dizziness: these are the first alert signals. To ignore these signs is to expose themselves to a progressive weakening of the immune system.
Repeated thermal shocks, a trap of air -conditioned environments
From heat wave to air conditioning: a trying yo-yo
Who has never spent their day alternating between outside at 35 ° C and air-conditioned office at 20-22 ° C? This brutal back and forth is a real shock for the mucous membranes of the respiratory tract. They are our first barrier against viruses.
The study by the University of Bordeaux in 2023 shows that these thermal shocks weaken these mucous membranes, which become dry, irritated, and therefore more vulnerable to viral infections such as colds or rhinopharyngitis.
When air conditioning turns to the source of infections
Poorly adjusted or poorly maintained, air conditioning can become a real microbes nest. Public Health France points out that poorly cleaned systems promote the proliferation of bacteria, notably Legionella, responsible for legionellosis, severe pulmonary infection.
And, as said above, the cold and dry air causes drying of the respiratory tract, which facilitates the penetration of viruses.
Gastroenteritis increasing in summer
Contrary to what one might think, gastroenteritis are not only winter affections. In summer, Public Health France recorded an increase of approximately 20 % of cases of acute gastroenteritis. This resurgence is often linked to heat which promotes bacterial proliferation in poorly preserved foods, and meals taken outdoors (picnics, buffets, barbecues) which are often less protected from contamination.
And, eating cold or poorly preserved increases the risk of contamination by bacteria like Salmonella, Campylobacter or Escherichia coli. These bacteria cause diarrhea, vomiting, abdominal pain and can seriously weaken the organism, especially if dehydration is added to the party.
Insect allergies and bites: the other face of summer
Summer pollens and respiratory allergies
Summer is also the holiday season, it is also that of the Pollens of Ambroisie, of Gramins and other dry herbs. The French Association for Allergies Prevention (AFPRAL, 2023) estimates that almost 20 % of French people suffer from seasonal allergies during this period, with rhinitis, conjunctivitis, even asthma attacks. These respiratory inflammations weaken the immune barrier, increasing the risk of infections.
Insect bites and inflammatory reactions
Mosquitoes, wasps, bees … These little summer companions can cause sometimes severe local reactions.
The inflammation they trigger tires the body and can complicate the healing of injuries or secondary infections.
Fatigue, rhythm of life and stress: aggravating factors
Often less restorative nights
The night heat disturbs sleep, and the lack of rest directly affects the ability of the immune system to fight against external aggressions.
Inserm (2022) stresses that chronic sleep deprivation can increase vulnerability to viral infections up to 15 %.
Summer work stress: an underestimated impact
If summer does not necessarily rhyme with relaxation for everyone, stress linked to the workload, heat or difficult conditions generates excessive production of cortisol.
This excess hormone is known to inhibit immune function according to Inserm, facilitating the occurrence of infectious diseases.
NAMELY
According to Public Health France, heat -related hospitalizations increased by 43 % in France between 2014 and 2022, particularly affecting active people under 65 years of age during periods of heat wave. The heat therefore does not spare the youngest, especially those who continue to work in summer.
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