339
Discussion
Comparisons of TEWL (g/m
2
/h) change from baseline between areas applied with LP and CB
in normal skin and psoriasis lesions
Normal skin
: At the end of a 4-week treatment, LP-treated area showed non-significant
decrease of TEWL (p=0.371) while CB-treated area showed non-significant increase of TEWL
(p=0.155) when compared to their baseline values. Comparing the mean difference values of pre/post
treatment from both areas, the mean difference of CB-treated area was significantly higher than the
mean difference of LP-treated area (p=0.011), therefore; LP showed better trend of decreasing TEWL
than CB in normal skin. This reflected that the normal skin was highly potential in adapting to any
moisturizers (in this case occlusive vs. emollient), no matter how a moisturizer exerts its action on the
skin. Draelos ZD found that the net decrease in TEWL after product application signified a moisturizer’s
advantage on the skin [23], based on this study, liquid paraffin (LP) was better than cream base (CB) in
terms of decrease TEWL. According to literature review, moisturizers can be subdivided by their
ingredients and mechanisms of action. In general, the main components included in a moisturizer are
emollients, humectant and occlusives. CB contains many effective emollients and humectants
including propylene glycol which is the most effective humectant. Even though, some humectants may
promote water loss from the skin by pulling water from the dermis to the epidermis [24], they are
efficient in hydrating the skin resulting the better physiologic state of the epidermis. Meanwhile, LP is
an occlusive [25, 26] which can reduce TEWL about 20-30% [27]; therefore, this study found the
decrease of TEWL.
Psoriasis lesions:
At the end of a 4-week treatment, LP-treated area showed non-significant
increase of TEWL (p=0.179) while CB-treated area showed non-significant decrease of TEWL
(p=0.996) when compared to their baseline values. Comparing the mean difference values of pre/post
treatment from both areas, there was no statistic difference (p=0.221). This study found the similar
Figure 1
The median value from 2 moisturizers readings for
transepidermal water loss (TEWL) from the normal skin and
psoriasis lesions objectively determined using the Vapometer
®
(Delfin Technologies Ltd., Kuopio, Finland). No significant
change was seen at 4 weeks compared with baseline.
Figure 2
The median value from 2 moisturizers readings for skin
hydration from the normal skin and psoriasis lesions objectively
determined using the Corneometer
®
CM 825
(Courage and Khazaka,
Cologne, Germany). Significant different was seen at 4 weeks
compared with baseline (P<0. 0001).
LP
CB
LP
CB
normal skin
psoriasis lesions
baseline
7.85
7.95
11.80
12.00
4 weeks
7.65
8.25
11.90
11.85
0
2
4
6
8
10
12
14
TEWL (g/m²/h)
LP
CB
LP
CB
normal skin
psoriasis lesions
baseline 32.19
29.87
6.98
8.23
4 weeks
34.00
33.39
10.62
14.69
0
5
10
15
20
25
30
35
40
Water content ofstratum
corneum (AU)
p<0.0001
p<0.0001
p<0.0001
p<0.0001
