356 JOURNAL OF COSMETIC SCIENCE
frequency.22 To reconfirm this relationship, they analyzed differences of the CPT value
(5 Hz) between the itch responder and non-itch responder groups. There was a significant
correlation between itch sensation and CPT values of 5 Hz. The itch responder group
showed significantly lower sensory perception value of 5 Hz than the non-itch responder
group.
QUANTITATIVE SENSORY TESTING (QST)
QST is a psycho-physical validated method that uses different stimuli of increasing intensity
to measure somato-sensory perception.23 This method allows evaluation of the participation
of small and large nerve fibers. Currently, QST is used mainly in neuropathic pain or
neuropathic pruritus to look for small-fiber neuropathies.24 The detection thresholds of heat
pain (HPT), vibration pain (VDT), and cold pain (CDT) can be tested using a Computer-
Assisted Sensory Examination (CASE) system IV (WR Medical Electronics Co., Maplewood,
MN, USA).25 A thermal electrode of 10 cm² is placed on the dorsum of the dominant hand
of the subject or elsewhere. The CASE IV software program automatically calculates the
pain ratings of heat pain (HP) HP 0.5, HP 5.0 and HP 5-0.5 with a quadratic regression
equation. HP 0.5 is defined as the midpoint between the smallest stimulus that created
pain and the largest no-painful stimulus. HP 5.0 corresponded to the stimulus that created
a rating of 5 from the subject. HP 5-0.5 was the difference between these two values. In
subjects with sensitive skin, the HPT is significantly lower (14.5 +/-2.8) than in the controls
(17.8 +/− 2.5) (p 0.001).26 Intermediate pain (HPT 5.0) is also significantly decreased.
CUTANEOUS THERMAL SENSATION
This psychophysical test is only based on the assessment of peripheral sensitivity to thermal
stimuli. This test involved the use of a thermal testing instrument—for example, the
Thermal Sensory Analyser (TSA 2001) manufactured by Medoc, Ramat Yishai, Israel—to
assess the thermal functional components of cutaneous nerve endings.16,27 The thermode
delivers thermal stimuli capable of heating or cooling the skin.
SKIN BIOPSIES
Histological analysis of skin biopsies in sensitive skin areas shows a decrease of intra-
epidermal nerve density, like in small-fiber neuropathies.28 However, it is difficult to use
this invasive technique routinely.
PARALLEL TESTS
The aim of many other tests is to evaluate skin properties which can be modified in
subjects with sensitive skin, but are not directly related to sensitive skin: trans-epidermal
water loss (TEWL), cutaneous pH, epidermal thickness (measured by ultrasonography,
optical microscopy, or confocal microscopy), skin penetrability (assessed with UV light),
molecular composition of stratum corneum (using confocal Raman microspectroscopy), or
others.12, 29–32 All these tests are commonly used in studies on sensitive skin, but they never
measure skin hypersensitivity.

357 Sensitive skin panels
QUESTIONNAIRES
It is obviously not possible to objectively determine the presence or absence of sensitive
skin,33 as sensitive skin is primarily a sensory disorder. However, the concept of diagnosing
sensitive skin through questionnaires emerged long after the development of reactivity
tests. While many scales have been proposed, they are often limited to use by a single
company, author, or even a single study.
Some scales have gained broader use because they were developed, validated, and translated
into multiple languages using the recommended methodologies. Examples include the
Sensitive Scalp Severity34 questionnaire for assessing sensitive scalp, and the Sensitive Scale
(SS) for evaluating sensitive skin in general.35More recently, the Burden of Sensitive Skin
(BoSS) scale was introduced to measure the impact of sensitive skin.36
SENSITIVE SCALE
The Sensitive Scale (SS-10) is a 10-item scale (Figure 1) that was initially validated across 11
countries and translated into multiple languages, involving a total of 2,966 participants..35
The internal consistency was high. Correlations with the dry skin type, higher age, female
gender, fair phototypes, and the Dermatology Quality of Life Index (DLQI) were found.
DLQI is a tool to evaluate the quality of life in patients with skin disorders.37 The 10-item
version is preferred over the 14-item version as it is quicker and easier to complete while
maintaining the same level of internal consistency. Additionally, the four excluded items
were found to be rarely relevant to patients. The mean initial score was around 37/100 (and
44/140 in the initial 14-item version). More recently, a SS-10 cut-off value of 12.7 to detect
sensitive skin was identified (with a sensitivity of 72.4% and specificity of 90.3%).38 For
practical reasons, we propose that a score greater than 13 on the SS-10 can be used as the
cut-off to diagnose sensitive skin, and a score greater than 5 can be used as the cut-off to
diagnose slightly sensitive skin.
3S QUESTIONNAIRE
The 3S questionnaire was created to assess sensitive scalp (Figure 2).34 The total score is
obtained by multiplying score severity of abnormal sensations by the number of these
sensations. The 3S questionnaire allowed discrimination between subjects with slightly
sensitive, sensitive, and very sensitive scalps. Itching and prickling were the most frequent
symptoms. The 3S questionnaire is a convenient and effective tool for investigating the
severity and symptomatology of the sensitive scalp.
BoSS QUESTIONNAIRE
The burden of a disease encompasses its physical, psychological, social, and economic
consequences. The BoSS questionnaire was specifically designed to evaluate all these
aspects in individuals with sensitive skin.36 Its development followed standardized
methodologies for creating and validating quality-of-life questionnaires, consisting of
three phases: design, development, and validation. The BoSS questionnaire demonstrated
strong psychometric properties, including excellent internal consistency and robust