343 Aging Skin Barrier
skin compared to younger subjects (Marks et al.,71 Kligman,72 Leveque et al.,25 Saijo et al.,73
Ghadially et al.85). See Table 1.
Hillebrand and Wickett74 reported TEWL data collected by G. Hillebrand, from 452
Chinese women between the ages of 10 and 70 years. ANOVA reveals statistically significant
differences between grouped ages (p =0.008). The 10–19 age group mean is significantly
less (p 0.05) than the 30–39, 40–49, and 50–59 age group means. The 60–70 age group
mean was also significantly less than the 30–39, 40–49, and 50–59 age group means. The
authors stated, “With these data, expressed in this way, we might conclude that skin barrier
function on the forearm of Chinese women living in Beijing decreases from the teens to the
forties (as gleaned from the 17% increase in TEWL) and thereafter increases.” However, the
authors also presented a scatter plot of the data showing all the individual data (Figure 4).
As the authors point out that while detailed statistical analysis indicates that TEWL is
lower in the 10–19-year-old age group, increasing in the 30–59-year-old age groups and
decreasing again in the 60–70-year-old age group the scatter plot indicates that there is
little or no clinical significance in these differences. Table I summarizes the effects of age
on TEWL reported by various authors.
Akdeniz et al.77 performed meta-analysis of 212 studies of TEWL primarily from the
forearm published between 1947 and 2017. The authors concluded that TEWL either does
not change or decreases slightly with age in general agreement with the studies discussed
above.
Possible age-related changes in skin penetration of organic compounds have been
investigated. Roskos et al. compared penetration of six drugs of differing polarity into the
skin of subjects 22–40 years of age and over 65 years old in vivo.78 Permeation rates for the
two most hydrophobic drugs, testosterone, and estradiol were not significantly different
between the two age groups but hydrocortisone, benzoic acid, acetylsalicylic acid, and
caffeine penetrated the skin of the older subjects at a significantly lower rate than younger.
Rougier et al. also reported that benzoic acid penetrated older skin significantly more
slowly than younger in vivo.27
Analysis of all these results leads to the somewhat surprising conclusion that basal SC
barrier function is relatively unaffected by age from childhood through late middle age
and then may begin to increase slightly sometime after age 60. It is notable that this
apparent improvement in baseline barrier function occurs in spite of the possible reduction
in SC barrier lipids discussed above. Rogers et al. point out that while lipids decrease
the ratio of ceramides to other SC structural lipids remain approximately constant.60 It is
also possible that skin permeation of some compounds through SC is slower because of
increased corneocyte area (see above). Rougier at al. found a negative correlation between
corneocyte size and the skin permeation rate for benzoic acid in vivo.27
AGING AND SENSITIVITY TO IRRITANTS
Most studies indicate that the reactivity of skin to irritants tends to decrease or at least does
not increase with age as one might expect. Bettley and Donoghue reported fewer reactions
to patch testing with soap in subjects 50 and older compared to subjects 10–49 years of
age.79 Grove et al. reported lower skin reactivity to a variety of irritants including dimethyl
sulfoxide, ethyl nicotinate and lactic acid in older subjects.56,80 Maibach and coworkers81,82 and
Robinson83 observed lower reactivity of older skin to sodium lauryl sulfate (SLS). Robinson
skin compared to younger subjects (Marks et al.,71 Kligman,72 Leveque et al.,25 Saijo et al.,73
Ghadially et al.85). See Table 1.
Hillebrand and Wickett74 reported TEWL data collected by G. Hillebrand, from 452
Chinese women between the ages of 10 and 70 years. ANOVA reveals statistically significant
differences between grouped ages (p =0.008). The 10–19 age group mean is significantly
less (p 0.05) than the 30–39, 40–49, and 50–59 age group means. The 60–70 age group
mean was also significantly less than the 30–39, 40–49, and 50–59 age group means. The
authors stated, “With these data, expressed in this way, we might conclude that skin barrier
function on the forearm of Chinese women living in Beijing decreases from the teens to the
forties (as gleaned from the 17% increase in TEWL) and thereafter increases.” However, the
authors also presented a scatter plot of the data showing all the individual data (Figure 4).
As the authors point out that while detailed statistical analysis indicates that TEWL is
lower in the 10–19-year-old age group, increasing in the 30–59-year-old age groups and
decreasing again in the 60–70-year-old age group the scatter plot indicates that there is
little or no clinical significance in these differences. Table I summarizes the effects of age
on TEWL reported by various authors.
Akdeniz et al.77 performed meta-analysis of 212 studies of TEWL primarily from the
forearm published between 1947 and 2017. The authors concluded that TEWL either does
not change or decreases slightly with age in general agreement with the studies discussed
above.
Possible age-related changes in skin penetration of organic compounds have been
investigated. Roskos et al. compared penetration of six drugs of differing polarity into the
skin of subjects 22–40 years of age and over 65 years old in vivo.78 Permeation rates for the
two most hydrophobic drugs, testosterone, and estradiol were not significantly different
between the two age groups but hydrocortisone, benzoic acid, acetylsalicylic acid, and
caffeine penetrated the skin of the older subjects at a significantly lower rate than younger.
Rougier et al. also reported that benzoic acid penetrated older skin significantly more
slowly than younger in vivo.27
Analysis of all these results leads to the somewhat surprising conclusion that basal SC
barrier function is relatively unaffected by age from childhood through late middle age
and then may begin to increase slightly sometime after age 60. It is notable that this
apparent improvement in baseline barrier function occurs in spite of the possible reduction
in SC barrier lipids discussed above. Rogers et al. point out that while lipids decrease
the ratio of ceramides to other SC structural lipids remain approximately constant.60 It is
also possible that skin permeation of some compounds through SC is slower because of
increased corneocyte area (see above). Rougier at al. found a negative correlation between
corneocyte size and the skin permeation rate for benzoic acid in vivo.27
AGING AND SENSITIVITY TO IRRITANTS
Most studies indicate that the reactivity of skin to irritants tends to decrease or at least does
not increase with age as one might expect. Bettley and Donoghue reported fewer reactions
to patch testing with soap in subjects 50 and older compared to subjects 10–49 years of
age.79 Grove et al. reported lower skin reactivity to a variety of irritants including dimethyl
sulfoxide, ethyl nicotinate and lactic acid in older subjects.56,80 Maibach and coworkers81,82 and
Robinson83 observed lower reactivity of older skin to sodium lauryl sulfate (SLS). Robinson
