Seborrheic dermatitis: Etiology, risk factors, and treatments:

In infants up to three months of age, SD involves the scalp, the face, and the diaper area.

“In infants up to three months of age, SD involves the scalp (termed “cradle cap”), the face, and diaper area.”

SD can affect the scalp as well as other seborrheic areas, and involves itchy and flaking or scaling skin, inflammation and pruritus.

“SD can affect the scalp as well as other seborrheic areas, and involves itchy and flaking or scaling skin, inflammation and pruritus.”

Incidence of SD in infants up to three months of age can be up to 42%.

“Incidence can be up to 42% [4–6].”

SD has a seasonal pattern, presenting more frequently during winter and improving usually during summer.

“SD has a seasonal pattern, presenting more frequently during winter, and improving usually during summer [5,25,26].”

Various intrinsic and environmental factors, such as sebaceous secretions, skin surface fungal colonization, individual susceptibility, and interactions between these factors, all contribute to the pathogenesis of SD and dandruff.

“Various intrinsic and environmental factors, such as sebaceous secretions, skin surface fungal colonization, individual susceptibility, and interactions between these factors, all contribute to the pathogenesis of SD and dandruff.”

New therapies for SD and dandruff include immune modulators such as topical calcineurin inhibitors and metronidazole, but their efficacy remains controversial.

“New therapies have also emerged including immune modulators such as topical calcineurin inhibitors, and metronidazole, but their efficacy remains controversial [5].”

The most common treatment for SD and dandruff is topical antifungal and anti-inflammatory agents.

“Because the main underlying pathogenic mechanisms involve Malassezia proliferation and local skin irritation and inflammation, the most common treatment is topical antifungal and anti-inflammatory agents (Table 3).”

In adults, SD is a chronic or relapsing condition, featured by erythematous patches, with flaky, large, oily or dry scales in sebum-rich areas such as face (87.7%), scalp (70.3%), upper trunk (26.8%), lower extremities (2.3%), and upper extremities (1.3%).

“On the other hand, in adults, SD is a chronic or relapsing condition, featured by erythematous patches, with flaky, large, oily or dry scales in sebum-rich areas such as face (87.7%), scalp (70.3%), upper trunk (26.8%), lower extremities (2.3%), and upper extremities (1.3%) [5,7,29].”

Malassezia are lipophilic yeasts that are found mainly on seborrheic regions of the body.

“Malassezia are lipophilic yeasts that are found mainly on seborrheic regions of the body [5,7,47].”

No clear differences were found in Malassezia levels between individuals with and without SD in the HIV/AIDS population, so an immune or inflammatory reaction could be the predisposition.

“Because no clear differences were found in Malassezia levels between individuals with and without SD in this population, it is likely that an immune or inflammatory reaction could be the predisposition [5,9].”

Both the incidence and severity of SD are associated with immune-suppression, particularly in HIV/AIDS patients.

“Both the incidence and severity of SD are associated with immune-suppression, particularly in HIV/AIDS patients.”

Epidermal barrier integrity, host immune response, neurogenic factors and emotional stress, and nutritional factors have all been shown to play a role in individual susceptibility to SD.

“Epidermal barrier integrity, host immune response, neurogenic factors and emotional stress, and nutritional factors have all been shown to play a role in individual susceptibility.”

Malassezia is detected on normal skin of the majority of healthy adults, making it a commensal organism.

“For example, Malassezia was detected on normal skin of majority of healthy adults, making it a commensal organism [2,5,26].”

Individual predispositions and host interactions with Malassezia, rather than the mere presence of Malassezia, contribute to SD and dandruff pathogenesis.

“While these observations support a pathogenic role for Malassezia in SD and dandruff, there is also strong evidence suggesting that individual predispositions and host interactions with Malassezia, rather than the mere presence of Malassezia, contribute to SD and dandruff pathogenesis.”

SD is more commonly seen in depressive disorders and emotional stress.

“SD is also more commonly seen in depressive disorders and emotional stress [5,16].”

Bilateral seborrhea has been observed in patients with unilateral Parkinsonism, suggesting that these sebum changes were likely regulated neuro-endocrinologically rather than purely neurologically.

“Bilateral seborrhea has been observed in patients with unilateral Parkinsonism, suggesting that these sebum changes were likely regulated neuro-endocrinologically rather than purely neurologically [5,26,91].”