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