The exact cause of seborrheic dermatitis is not known for sure.
In adults, seborrheic dermatitis affects nearly 5% of the general population.
SD is slightly more common in men than in women.

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In infants, eczema on the scalp is often accompanied byatopic dermatitis.
Having a visible rash can really have an impact on self-esteem, particularly during adolescents.
Causes
The precise cause of seborrheic dermatitis is not well known.
But, experts surmise that genes and hormones are very apt to play a role in its development.
This is thought to happen when a specific key in of organismcalled Malasseziabegins to grow and multiply very quickly.
These include:
Diagnosis
Seborrheic dermatitis is said to be an easy condition to diagnose.
The dermatologist will do an examination to observe the affected areas.
Wikramanayake TC, Borda LJ, Miteva M, Paus R.Seborrheic dermatitis-Looking beyond Malassezia.Exp Dermatol.
2019;28(9):991-1001. doi:10.1111/exd.14006
National Eczema Association.Seborrheic dermatitis.
Del Rosso JQ.Adult seborrheic dermatitis: a status report on practical topical management.J Clin Aesthet Dermatol.
2011;4(5):32-38.
Institute for Quality and Efficiency in Health Care (IQWiG).
Seborrheic dermatitis: Overview.
National Eczema Association.An overview of different types of eczema.
Cleveland Clinic.Seborrheic Dermatitis: Diagnosis and Tests.
Gul A., Karaaslan O, Colgecen E.Personality traits and common psychiatric conditions in patients with seborrheic dermatitis.
Archives of Clinical Psychiatry (Sao Paulo).