Introduction
Environmental factors play a significant role in seborrheic dermatitis (SD) and
dandruff. High temperatures and high humidity are primary triggers for SD exacerbations, while low temperatures, low
UV index, and high humidity also increase the risk of SD development in temperate and humid climates. [1,2] Environmental factors also impact the distribution of Malassezia species, several of which have been isolated from
Seborrheic Dermatitis lesions.[3–5] Environmental Factors Influencing Seborrheic Dermatitis and Dandruff
Climate and Weather Conditions
In addition to patient characteristics like age and gender, geographical differences
also affect the clinical presentation of Seborrheic Dermatitis (SD). Recent studies indicate a strong association
between Malassezia species and the development of Seborrheic Dermatitis, as these microorganisms thrive in the
lipid-rich environment of seborrheic skin. [2,6–8] Study of Thai patients with Seborrheic Dermatitis, which
identified seasonal factors, particularly hot weather, as primary triggers for SD exacerbation.[1] Study was
conducted to assess the monthly and seasonal frequency of seborrheic dermatitis (SD) in Istanbul, Turkey. It aimed
to explore the relationship between SD frequency and meteorological data, including average temperature (°C),
average humidity (%), average sunshine duration, and solar radiation per month. The findings indicate that
environmental factors such as low temperatures, low UV index, and high humidity significantly increase the risk of
SD development in a temperate and humid climate.[2] Pollution, and Urbanization
The World Health Organization (WHO) identifies air pollution, both outdoor and indoor,
as a leading environmental health risk. Exposure to these pollutants, from sources like wildfires and factory
emissions, damages the skin barrier and induces oxidative stress, leading to inflammatory skin and scalp diseases,
autoimmune conditions, and skin tumors. [[9–11] Multicenter study from China found that higher city pollution level
PM10 increased the risk of seborrheic dermatitis symptoms. Higher levels of urbanization and living close to heavily
trafficked roads were also associated with seborrheic dermatitis symptoms.[11] Similarly, a prospective cohort
analysis of 193,995 participants identified 3,363 SD cases, revealing a significant link between higher air
pollutant concentrations (PM2.5, PM10, NO2, and NOX) and increased SD risk, particularly in younger males,
socioeconomically deprived individuals, smokers, daily alcohol consumers, and those with regular physical activity.
The findings underscore the need to mitigate environmental exposures to reduce SD risk in the elderly.[12] Dietary Factors
A cohort study found that several dietary factors were associated with seborrheic
dermatitis (SD), suggesting that diet may influence the disease’s course. Foods such as white bread, rice, pasta,
non-acidic fruits, leafy green vegetables, roasted or fried nuts, raw nuts, and coffee were linked to SD.
Conversely, citrus fruits and vegetables were reported to alleviate SD symptoms, while spicy food, sweets, fried
food, dairy products, and citrus fruits were noted as aggravators. [13–16] Stress and Psychological Factors
Stress often triggers episodes of seborrheic dermatitis, as noted in numerous reviews
on the topic. A study was conducted that investigated the relationship between psychological stress and seborrheic
dermatitis (SD). Conducted in two phases, it involved 82 patients who completed questionnaires assessing their SD
episodes, stress levels, and psychological states. Results showed that 82% had scalp involvement, and stress was
identified by patients as a key trigger for SD episodes. A significant correlation was found between stress and SD
exacerbations, with higher anxiety scores among those linking stress to their SD episodes.
Additionally, patients with facial involvement exhibited higher depression scores. The
study highlights stress as a major factor in SD flare-ups and suggests that managing stress could be crucial in
treating SD.[17] These factors may also play a role in the development or worsening of seborrheic dermatitis.[18,19]

Managing stress is crucial, but it should be combined with effective topical treatments
for seborrheic dermatitis, such as selenium sulfide, to achieve the best outcomes. [20–22] Selenium sulfide serves as a therapeutic agent in various dermatological conditions and
constitutes the active component in anti-dandruff shampoo formulations. Beyond its role in dandruff management, it
is also employed in the treatment of tinea versicolor.
Selenium Sulfide: Mechanism of Action and Benefits
Multifaceted Mechanism of Action
Selenium sulfide serves as a therapeutic agent in various dermatological conditions and
constitutes the active component in anti-dandruff shampoo formulations. Beyond its role in dandruff management, it
is also employed in the treatment of tinea versicolor. [23–27] Selenium sulfide exhibits a multifaceted action that
makes it a versatile and effective therapeutic agent in dermatology. Known for its potent antifungal properties, it
disrupts fungal cellular oxygen metabolism, leading to increased production of reactive oxygen species (ROS), which
can replace synthetic fungicides.[28] Additionally, selenium sulfide acts as a cytostatic agent by reducing
corneocyte production and slowing epidermal cell turnover, thereby alleviating conditions like dandruff and
seborrheic dermatitis.[23] It also possesses antibacterial and antiseborrheic properties, enhancing its therapeutic
efficacy.
Environmental and climatic factors, such as humidity and temperature fluctuations, can
exacerbate seborrheic dermatitis and dandruff by creating an optimal environment for the proliferation of Malassezia
species. [2] These conditions can increase the activity of sebaceous glands, leading to an
overproduction of sebum, which, in turn, promotes fungal growth and skin irritation. Selenium sulfide’s ability to
interfere with fungal metabolism and reduce cell turnover is particularly beneficial in such conditions, as it helps
to counteract the increased fungal activity and skin irritation triggered by these environmental factors.[29] This
dual action not only addresses the underlying fungal cause but also mitigates the symptoms exacerbated by climatic
influences, making selenium sulfide a comprehensive treatment option for managing seborrheic dermatitis and dandruff
in various environmental conditions.
Clinical Efficacy and Safety Profile
There is no significant difference in effectiveness or adverse effects between selenium
sulfide 1.8% shampoo and ketoconazole 2% shampoo for treating pityriasis versicolor. Given its similar efficacy,
cost-effectiveness, and minimal side effects, selenium sulfide 1.8% shampoo is a viable treatment option for
dermatological conditions such as seborrheic dermatitis, dandruff, and pityriasis versicolor. In particular, using
selenium sulfide shampoo for maintenance therapy in managing these chronic recurring conditions can offer economic
benefits. Further research is needed to determine the optimal duration and methods of application to improve
treatment outcomes.[30] Conclusion
Seborrheic dermatitis (SD) is significantly influenced by environmental factors such as
climate, pollution, and lifestyle. High temperatures and humidity, low temperatures, UV exposure, pollution, and
urbanization exacerbate SD. Additionally, diet, stress, and psychological factors play critical roles in its
development and exacerbation.
Selenium sulfide is an effective therapeutic agent for SD and related conditions. Its
multifaceted action includes potent antifungal, antibacterial, and antiseborrheic properties. It disrupts fungal
cellular metabolism, reduces corneocyte production, and slows epidermal cell turnover. Selenium sulfide’s efficacy,
cost-effectiveness, and minimal side effects make it a valuable option for managing chronic conditions like SD,
dandruff and pityriasis versicolor.

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