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broadly contain different ingredients and patients’ response can vary considerably. Kattipathanapong P
et al compared various kinds of moisturizers available at the IOD of healthy skin and found that the
efficacy of liquid paraffin and cream base is comparable to that of other expensive moisturizers.
Therefore, in the present study, the author evaluated the clinical outcomes of the two moisturizers
when applied to normal skin and psoriasis lesions among mild plaque psoriasis patients.
Methods
This study was a prospective, randomized, open-labeled with blinded outcome evaluation
study, comparing skin moisturizing efficacy of liquid paraffin (LP) with cream base (CB) applying on
normal skin and areas of lesions in psoriasis patients. The study was carried out at the Outpatient
Department of the Institute of Dermatology. This study was approved by the Institutional Review Board
of the Faculty of Medicine Siriraj Hospital, Mahidol University, and of the Institute of Dermatology,
Bangkok, Thailand.
Study population
Eligible subjects were individuals aged 18 years or older, who were diagnosed with mild
plaque type psoriasis (Psoriasis Area and Severity Index (PASI) score less than 10). Participants were
excluded if they had chronic diseases such as liver or kidney diseases, or were allergic to liquid paraffin
or cream base. All subjects provided written-informed consents before enrollment into the study.
Interventions
For each subject, the first author determined an area of normal skin with the size of
4 cm x 4 cm on the left side of the body and the other on the right, trying to be as symmetrical as
possible. By the same manner, an area of psoriasis lesions was also determined on each side of the
body. Each study area was marked with permanent ink. The study medications contained cream base
0.5 g or liquid paraffin 0.5 ml to be applied in each area (4 cm x 4 cm) by the participants. Each subject
was then randomly assigned to apply liquid paraffin to the designated areas of normal skin and
psoriasis lesions on one side of the body (either left or right) and cream base to the other. The study
medications were applied twice daily for 4 weeks. Other medications were administered at the
discretion of the attending dermatologist.
Outcomes
Study outcomes were transepidermal water loss (TEWL) and skin hydration, measured in
normal skin and psoriasis lesions areas at baseline, at 60 minutes after applying the first dose, and at
the end of the 4
th
week. Measurements were performed by noninvasive bioengineering methods.
Transepidermal water loss (TEWL), a parameter of the water barrier function of the stratum corneum
(SC), was measured using close-chamber evaporimeter (Delfin Technologies Ltd., Kuopio, Finland) in
the unit of g/m
2
/h [19]. Skin hydration was measured using the corneometer
®
CM 825
(Courage and
Khazaka, Cologne, Germany), which measures electrical capacitance of the skin surface expressed in
arbitrary units (AU) [20]. Prior to every measurement, subjects stayed in the testing room for at least
