quite unsightly. Skin moisturizers (humectants, emollients) form temporary lipid films on the
skin surface and below that act to diminish the rate of evaporative water loss.
Other than moisturizer applications, a number of advisory cautions have been generated by
dermatologists. Some are:
• Washing with lukewarm or cold (not hot) water
• Using soap sparingly and rinsing off quickly
• Avoiding deodorant/antibacterial soaps
• Gently patting skin dry (and immediately using a moisturizer)
• Washing new clothing before wearing
• Avoiding fabric/dryer sheets
• Avoiding wool and tight clothes (they increase itching)
• Wearing cotton clothing as much as possible
• Minimizing scratching and rubbing
• Applying cool compresses or “baggies” of ice cubes to itch areas for relief
• Avoiding applying cosmetics with fragrances
• Avoiding applying cosmetics on irritated skin, except moisturizers
A key aspect of dry skin dermatology is Transepidermal Water Loss (TEWL). Instruments
such as the Tewaneter TM 300 measure TEWL and thus the barrier function of treated versus
untreated skin. From these, the efficacy of the skin moisturizer can be determined as soon as
the film dries and for several hours thereafter. This is an indispensable assay in formula
development work.
A fair number of instruments are now available for TEWL studies; each has its own
“personality.” They replace the taped-on patch tests, where pre-weighed absorbent pads
are applied to fixed areas of treated and untreated skin area. On removal they are immediately
checked for moisture content using a Karl Fisher assay (a classic titration method
in analytical chemistry that uses coulometric or volumetric titration to determine trace
amounts of water in a sample). For reproducible results, volunteers should be stationed
in constant temperature and humidity chambers.
More sophisticated clinical laboratories may back up TEWL studies with chemical
patch tests, typically on the hairy (volar) forearm or back of subjects. In one, up to
Despite its name, Kiss My
Face Light Moisturizing
Lotion with Lavender &
Shea Butter is for the body.
The calming Lavender Shea
formula is blended with
nourishing antioxidants to
help soften, hydrate and
soothe skin.
0.10% solutions of sodium
lauryl sulfate (SLS) are
applied for 24 hours (SLS
is a well know mild skin
irritant). The treated skin is
then checked for erythema,
either visually or with a
quantifying device, such as
a Minolta Chromameter
(Moorman Instruments). A
low vascolar response suggests
good protection. Other
chemicals, such as sodium
hydroxide (NaOH) and
dimethyl sulfoxide (DMSO),
have also been utilized.
Perhaps the most persuasive
tests involve applying
prospective products on
volunteers and noting the
results, both visibly and
tactically over several weeks.
Ideally, the treated dry skin
should lose its rough texture
and flakiness without the
skin becoming irritated,
sensitized or otherwise traumatized. The product should spread on the skin smoothly, without giving the
consumer any sensations of stickiness, greasiness, coloration or shine. It should dry rather quickly, without
causing consumers to unduly delay putting on their clothes. Some products promise significant improvement
of skin texture in five days.
February 2019 SPRAY 35
Allergic Contact Dermatitis testing. (Photo from PA Centre of Dermatology)