Skin Irritancy Tests Clinical Trial
Official title:
Determination of Sensitive Skin in a Mexican Population by Lactic Acid Testing and Its Analysis Through Biophysical Measures
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.
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.
;
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Investigator, Outcomes Assessor), Primary Purpose: Diagnostic