The terms “sensitive skin”, “reactive skin”, “irritable skin” are used for long years by the cosmetic industry to describe several symptoms which make it possible to distinguish these cutaneous conditions but which can also be combined with each other, sometimes being confused to precisely define the desired target.

Since 2017, sensitive skin has an international consensus definition proposed by the IFSI [International Forum for the Study of Itch] which defines it as “a syndrome manifested by the occurrence of unpleasant sensations (prickling, burning, pain, pruritus) in response to stimuli that would not normally cause such sensations. These unpleasant sensations cannot be explained by damage due to a specific skin disease. The skin may appear normal or be accompanied by erythema. Sensitive skin can occur in any skin location and especially on the face”.

The “sensitive” skin syndrome linked to a hyper-reactivity of the skin may be favored in the presence of certain factors such as environmental parameters (temperature variation, pollution, cold, heat, wind…), chemical (cosmetics, pollution), psychological (stress), internal (hormones, alcohol, spices…)

In order to select volunteers with “sensitive” skin, it is possible to refer to the ARPP definition (July 2019) which takes into account, in particular, the declaration by subjects of a recent and repeated history of functional skin discomfort symptoms.

As sensitive skin being a subjective syndrome defined by the occurrence of sensations, diagnosis can be made by asking subjects about the sensations perceived and the mode of onset. Scales, such as the 10-question Sensitive Scale (Misery & al, 2014) is the most widely used to help diagnose sensitive skin, but some sponsors have also their own criteria for including subjects with sensitive skin.

Sensitive skin is very common since it affects about half of the French population, more often women (60%) than men (40%) (Misery & al. , 2018).

They mainly affect the face, although other areas may be affected such as the body and scalp.

An European study showed differences in the prevalence of sensitive skin between countries but also due to cultural and linguistic differences.

Sensitive skin is mainly found on the face (85%) but can also be present on the hands (57%), scalp (36%) and neck (27%).

The face is the area most often affected due to direct exposure to environmental factors (sun, wind, etc.) but also to the use of cosmetics and due to the high nerve density in this area.

Sensitive skin has an impact on quality of life, at least in its psychological dimension. Several quality scores show this significant relationship between the fact of having sensitive skin and the impairment of quality of life. This impact can be assessed by the generic questionnaire for studying quality of life in dermatology: Dermatology life Quality Index (DLQI) but also by a specific quality of life questionnaire for subjects with sensitive skin, the Burden of Sensitive Skin (BoSS) questionnaire.

In sensitive skin, the direct consequence of the alteration of the skin’s barrier function and its lack of hydration is that the tolerance threshold is lowered: the skin becomes more sensitive to irritants and external stimuli. Indeed, as the skin’s barrier function is less effective, the penetration of aggressors is facilitated. This results in an inflammatory response leading to the release of pro inflammatory cytokines. This inflammatory mechanism explains the clinical signs such as redness and heat sensations.

In order to respond to the problem of skin sensitivity, which corresponds to a hyper-reactivity resulting from a lowering of the tolerance threshold, IEC can offer different protocols such as:

• A 21-day In Use Test on at least 20 subjects with “sensitive” skin according to the ARPP definition, combined with questionnaires and quality of life perception scales.
• Evaluation of the skin’s barrier function [measurement of the Trans-Epidermal Water Loss] which, once restored, hinders the penetration of potentially irritating agents, thus increasing the skin’s tolerance threshold.
• The measurement of certain neuro-mediators secreted by the superficial nerve endings and pro-inflammatory cytokines, the reduction of which corresponds to a reduction in skin reactivity.
• The scoring of the overall intensity of prickling [immediate or long-term effect] with the Stinging Test [lactic acid].

For a global multi-ethnic and cultural approach, these tests can be performed in our 8 test centers in France, Bulgaria, South Africa and Asia (Japan, Singapore, Korea and China).

The claims corresponding to this type of skin such as “suitable for sensitive skin”, “short and/or long-term soothing effect” ….. must result in a reduction in the perception of discomfort, ideally associated with an improvement in the biometric parameters mentioned above. www.iecfrance.com

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