Determination of Sensitive Skin and Its Biophysical Response in a Latin-American Population
Condition: Skin Irritancy Tests
MeSH terms: Hypersensitivity
Study type: Interventional
Phase: Phase 4

Summary: 
      Sensitive skin syndrome is a frequent self-diagnosed entity that has not been previously
      described in a Latin-american population. One hypothesis to its development is an alteration
      of the barrier function of the skin. The aim of the study is to describe the frequency of
      sensitive skin in a mexican population detected through the lactic acid test, and to explore
      its response through biophysical measures (colorimetry, transepidermal water loss (TEWL) and
      capacitance). The prevalence of this syndrome in studied populations is approximately 50%.
      Considering racial skin differences, the investigators would expect at least a 20%
      prevalence.

      For this purpose, the investigators would need a minimum of 243 healthy volunteers, 18 years
      or older, with previous informed consent, to whom the lactic acid test will be performed. The
      investigators will record any unpleasant sensation graded in a Visual Analog Scale (VAS) of
      10 points, colorimetry, TEWL and capacitance before the test and at 3, 5, 8 and 10 minutes
      after the lactic acid test.
    

Detailed description: 
      Sensitive skin is defined as the presence of itching, stinging, burning or other unpleasant
      sensations due to external factors (such as light, heat, cold, air, cosmetic products, soap,
      water and even emotional and hormonal factors). By definition it is a subjective syndrome,
      where there are no clinical signs, making it a self-diagnosed entity. Previous
      community-based studies, mostly in caucasians, have found a high prevalence in general
      population. Nonetheless, to date there are only a few studies and with a small amount of
      subjects that have applied an objective test to identify this syndrome, and even fewer have
      explored the possible alterations associated to it.

      The investigators aim to describe the frequency in a hispanic population, and further explore
      the presence of alterations in the barrier function through measurement of TEWL and
      capacitance, as well as possible subclinical erythema (a* axis of colorimetry) or variations
      due to skin pigmentation (L* axis).

      The volunteers in the study will be randomized to receive in one nasolabial fold 10% lactic
      acid solution, and placebo (0.9% saline solution) in the other to act as the control. The
      investigators will be grading any unpleasant sensation in a 10-point scale (VAS) at 4
      different time intervals: 3, 5, 8 and 10 minutes. The investigators will be measuring
      colorimetry (ChromaMeter CR-300 (Minolta, Japan)), TEWL (Evaporimeter DermaLab (Cortex
      Technology, Denmark)) and capacitance (Corneometer DermaLab Moisture Module (Cortex
      Technology, Denmark)) before performing the test, and at 3, 5, 8 and 10 minutes after it.
      These time intervals have been previously determined according to previous reports where the
      maximum intensity of the response is obtained in the first 5 minutes, and after 10 minutes
      the response gradually diminishes.

      Statistical analysis will be performed with square chi test, t-test or U-Mann-Whitney,
      according to the parametric or non-parametric distribution of the values. All tests will be
      performed using the JMP software 8.0 (Cary, NC, USA) at 95% of confidence, statistical
      significance at 5% with 80% power.
    

Intervention name(s): 10% lactic acid test; Placebo
Intervention type(s): Procedure; Procedure
Intervention description(s): To each subject, 10% lactic acid is applied to one nasolabial fold. This will be performed under humidity, temperature and pH control to avoid influence of these variables in the result of the test.; To each subject, 0.9% saline solution will be applied to the contralateral nasolabial fold. This will be performed under humidity, temperature and pH control to avoid influence of these variables in the result of the test.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Diagnostic
Keywords: Sensitive skin; Lactic acid test; Transepidermal water loss; Colorimetry; Capacitance