Specific causes of Seborrhoeic Dermatitis are not known. Current theories for the cause of the disease include:
-A weakened immune system,
-The lack of specific nutrients (for example zinc),
-Or issues with the nervous system.
Seborrhoeic dermatitis may involve an inflammatory reaction to a proliferation of a form of the yeast Malassezia, though this has not been proven.
The main species found on the scalp is Malassezia globosa, others being Malassezia furfur (formerly known as Pityrosporum ovale) and Malassezia restricta.
The yeast produces toxic substances that irritate and inflame the skin. Patients with seborrhoeic dermatitis appear to have a reduced resistance to the yeast.
However, the colonization rate of affected skin may be lower than that of unaffected skin.
Only saturated fatty acids (FAs) have been shown to support Malassezia growth. It has also been shown that while number density of M. globosa and M. restrictado
not directly correlate to dandruff presence or severity, removal correlates directly with amelioration of flaking.
Furthermore, in dandruff-susceptible individuals pure oleic acid, an unsaturated FA and Malassezia metabolite, induces flaking in the absence of Malassezia by direct effects on the host skin barrier.
These findings support the following hypothesis:
-Malassezia hydrolyze human sebum, releasing a mixture of saturated and unsaturated fatty acids. They take up the required saturated FAs, leaving behind unsaturated FAs. The unsaturated FAs penetrate the stratum corneum. Because of their non-uniform structure, they breach the skin's barrier function. This barrier breach induces an irritation response, leading to dandruff and seborrheic dermatitis.
Genetic, environmental, hormonal, and immune-system factors have been shown to be involved in the manifestation of seborrhoeic dermatitis. Seborrhoeic dermatitis may be aggravated by illness, psychological stress, fatigue, sleep deprivation, change of season and reduced general health.
In children, excessive vitamin Aintake can cause seborrhoeic dermatitis. Lack of biotin, pyridoxine(vitamin B6) and riboflavin(vitamin B2) may also be a cause. Those with immunodeficiency (especially infection with HIV) and with neurological disorders such as Parkinson's disease(for which the condition is an autonomic sign) and stroke are particularly prone to it.
-A weakened immune system,
-The lack of specific nutrients (for example zinc),
-Or issues with the nervous system.
The main species found on the scalp is Malassezia globosa, others being Malassezia furfur (formerly known as Pityrosporum ovale) and Malassezia restricta.
The yeast produces toxic substances that irritate and inflame the skin. Patients with seborrhoeic dermatitis appear to have a reduced resistance to the yeast.
However, the colonization rate of affected skin may be lower than that of unaffected skin.
Only saturated fatty acids (FAs) have been shown to support Malassezia growth. It has also been shown that while number density of M. globosa and M. restrictado
not directly correlate to dandruff presence or severity, removal correlates directly with amelioration of flaking.
Furthermore, in dandruff-susceptible individuals pure oleic acid, an unsaturated FA and Malassezia metabolite, induces flaking in the absence of Malassezia by direct effects on the host skin barrier.
These findings support the following hypothesis:
-Malassezia hydrolyze human sebum, releasing a mixture of saturated and unsaturated fatty acids. They take up the required saturated FAs, leaving behind unsaturated FAs. The unsaturated FAs penetrate the stratum corneum. Because of their non-uniform structure, they breach the skin's barrier function. This barrier breach induces an irritation response, leading to dandruff and seborrheic dermatitis.
Genetic, environmental, hormonal, and immune-system factors have been shown to be involved in the manifestation of seborrhoeic dermatitis. Seborrhoeic dermatitis may be aggravated by illness, psychological stress, fatigue, sleep deprivation, change of season and reduced general health.
In children, excessive vitamin Aintake can cause seborrhoeic dermatitis. Lack of biotin, pyridoxine(vitamin B6) and riboflavin(vitamin B2) may also be a cause. Those with immunodeficiency (especially infection with HIV) and with neurological disorders such as Parkinson's disease(for which the condition is an autonomic sign) and stroke are particularly prone to it.
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