dermatitis severity score measured with Seborrheic
Area Severity Index (SASI) (Olina et al, 2015). In
contrast, Park’s study observed male sex, duration of
disease of more than 7 years, and history of acne
vulgaris as the influencing factors of scalp seborrheic
dermatitis occurrence (Park et al, 2016).
Bivariate analysis showed a significant
relationship between duration of sun exposure to
seborrheic dermatitis severity score (p<0.05), with a
correlation coefficient of -0.322, showing an
inversely proportional relationship where longer
duration of sun exposure is related to lower
seborrheic dermatitis severity score. Nevertheless, a
coefficient of 0.322 shows a weak correlation. The
role of sunlight, including ultraviolet rays, in
seborrheic dermatitis is still controversial. Currently,
no other studies have investigated the direct
relationship between duration of sun exposure and
seborrheic dermatitis severity score. The factors
associated with seborrheic dermatitis which have
been extensively studied include Malassezia,
sebaceous glands activity, and skin defenses.
The findings of this study are corroborated by
previous studies on the effect of ultraviolet irradiation
on Malassezia or Pityrosporum ovale fungi. Mayser
and Pape’s study showed UVA and UVB irradiation
had significant inhibitive effects on Malassezia
growth (Masyer et al, 1998).
Their findings became
the foundation of using UVB phototherapy as a
treatment method for seborrheic dermatitis,
especially for patients with large or recalcitrant
lesions, although this modality has not been proven
by randomized trials (Naldi, 2009). Moreover,
Mayser and Pape’s findings on sun exposure’s effect
on sebaceous glands, skin condition, skin temperature
changes, and sweat production were not consistent
with the results of other previous works. The effects
of ultraviolet irradiation on sebaceous glands and
sebum production have been extensively studied.
Akimoto conducted a study on the sebocytes of
guinea pigs, and found increased cell proliferation
and sebum production after UVB irradiation (Setiati,
2006). On the contrary, Lee’s study on human
sebocytes found irradiation with UVB, UVA, and
other components of sunlight did not cause significant
increase nor decrease in sebum production (Lee et al,
2015). Although seborrheic dermatitis occurrence is
strongly associated with sebaceous glands activity,
excessive sebum production is not an independent
etiological factor of seborrheic dermatitis (Collins et
al, 2012) (Goldberg et al, 2013). In general,
seborrheic dermatitis develops due to changes in lipid
compositions on the skin surface, providing favorable
conditions for the colonization of certain
microorganisms. Excessive sun exposure and
ultraviolet irradiation are believed to disturb the
skin’s defenses, supporting the development of
seborrheic dermatitis (Akitomo et al, 2003).
Akimoto’s study highlighted how ultraviolet rays can
oxidize squalane, a form of lipid found on the skin
surface, to squalane peroxidase which can irritate the
skin and disturb its defenses (W&S Market Research,
2016).
A few limitations may influence the results of our
study, such as the use of sun exposure duration as the
sole indicator of sun exposure. According to Koster,
in order to measure sun exposure, thorough
observation of objective and subjective factors is
needed. In addition to duration, observations of the
time of exposure, ultraviolet ray intensity, exposed
body parts, and sun protection habits should be
made.
9
Furthermore, the subjects in our study mostly
had mild seborrheic dermatitis, and none of the
subjects had severe seborrheic dermatitis, thus the
conclusion on the relationship between sunlight and
seborrheic dermatitis based on the findings of this
study should be interpreted with caution. Thus, an
important component to include in future
investigations is an equal distribution of different
levels of seborrheic dermatitis severity. Our study did
not include other factors aside from the duration of
sun exposure as variables, which lead to the
possibility of our results being affected by other
confounding factors, due to seborrheic dermatitis’
multifactorial nature. This limitation suggests an
opportunity for future multivariate research to study
the various factors that can influence the severity of
scalp seborrheic dermatitis.
5 CONCLUSION
The evidence from the current study suggests a
significant negative correlation, albeit weak, between
the duration of sun exposure and scalp seborrheic
dermatitis severity score. Our study was limited by
the large amount of subjects (89.7%) with mild
seborrheic dermatitis, thus further investigations
including all levels of seborrheic dermatitis severity
are needed.
REFERENCES
Akitomo, Y., Akamatsu, H., Okano, Y., Masaki, H., &
Horio, T., 2003. Effects of UV irradiation on the
sebaceous gland and sebum secretion in