Stress was studied throughout the 20th century by Hans Selye, an Austrian endocrinologist based in Canada.
In the 1950s, it was defined as the set of physical and psychological reactions triggered by the body to adapt to an event.
This definition was refined in the 1970s when it was discovered that every event triggers a specific response from the body, but also, in the background, a non-specific response: the General Adaptation Syndrome, consisting of an alarm phase, a resistance phase, and an exhaustion phase.
This is the sympathetic division of the autonomic nervous system (increased respiratory and heart rates, muscle tension, and energy supply) that is responsible for stress adaptation. Conversely, the parasympathetic pathway is responsible for rest and relaxation.
Not all stress is the same: “good stress” does not lead to phases of resistance or exhaustion, but the body’s non-specific response begins in the same way as it would under less favourable conditions. “Bad stress” has long-term effects, leading to the development of chronic stress.
“Fight if you can win, or flee” Hans Selye
The phases of the General Adaptation Syndrome correspond to hormonal fluctuations
an adrenaline spike occurs in response to a shock during the alarm phase;
an elevated cortisol level is observed during the resistance phase, leading in particular to increased levels of blood sugar, triglycerides and cholesterol;
a collapse of all hormonal secretions marks the exhaustion phase.
The symptoms of stress are numerous and varied but always result in a weakening of the immune system.
Some specific cases: post-traumatic stress follows an accident, an assault or a disaster, and burnout is characterised by physical and mental exhaustion due to prolonged exposure to stress.
In general, physiological reactions related to stress can be divided into two categories:
Nervous symptoms of stress
Behaviours: aggression, irritability, demotivation, loss of confidence, isolation, escapism or even addictions, anxiety, depressive tendencies…
Sleep disorders
Difficulties with concentration and memory
Physical manifestations of stress
Fatigue
Headaches
Muscle tension
Spasmophilia
Chronic infections
Digestive disorders: nausea, spasms, ulcers…
Skin disorders: eczema, psoriasis, shingles… and hair loss
Gynecological disorders: amenorrhea, decreased libido…
Cardiac disorders: tachycardia, high blood pressure, heart attack…
Finally, it is important to distinguish between stress in the broad sense and oxidative stress, which we focus on extensively in cosmetics: linked to an excessive presence of free radicals in the body compared to the available antioxidants, it is one of the consequences of chronic stress exposure but depends on many other environmental factors.
So, if…
“Stress occurs when a person’s personal coping resources and strategies are overwhelmed by the demands placed upon them.” World Health Organization (WHO), 2001
… how can we naturally strengthen our resilience against stress?

















