Seborrheic dermatitis: definition, causes and treatment

By Cristiano Antonino On Apr 27, 2023

Seborrheic dermatitis is a dermatological disorder resulting from a malfunction of the sebaceous glands and an incompetence of the immune system

In these conditions some fungal strains (genus Malassezia) already normally present on the skin, are transformed from commensals into opportunistic pathogens.

The disease, also known as seborrheic eczema, is chronic and recurring and presents with signs and symptoms that are also very common to other pathologies such as: reddened skin, scaling, dandruff and the presence of fairly painful papules in the most severe cases.

Seborrheic dermatitis affects up to 1-3% of the world population, preferring the more westernized areas and industrialized countries in general.

This is because, among the risk factors already mentioned (genetic, immune and hormonal), environmental ones (smog and pollution) also seem to be determined.

It is considered an intermittent disease as it can affect the same subject at certain times of the year, as well as in certain phases of life, and then regress on its own without ever disappearing.

It has been found that the most affected subjects are men between the ages of 30 and 40 and children, especially in the first 3 months of life.

In this case we speak of seborrheic dermatitis on infants (whose typical manifestation is the famous cradle cap).

What is seborrheic dermatitis

Seborrheic dermatitis mainly affects the face and scalp (in particular the hairline, ears, folds between the nose and lips, eyelids and eyebrows), but it is not uncommon to find it also in other areas of the body where the presence of sebaceous glands is high, such as example in the hollow of the armpits, between the shoulder blades, on the sternum and genital area or in the ear canal.

An overactivation of the sebaceous glands, with a consequent increase in the production of sebum, would trigger an imbalance in the proliferation of some skin fungi with a consequent cascade reaction that leads to inflammation of the tissue.

The affected areas therefore appear reddened and scaly, a bit like after a sunburn

When this affects the scalp, however, an excessive amount of dandruff and scabs are generated, yellowish in color and greasy, which make the hair dry and frizzy, giving the subject a perennial feeling of dirty scalp.

Often the symptoms are also associated with localized itching and burning.

Although chronic, seborrheic eczema should not cause particular concern: it is not a health hazard, nor is it contagious.

However, it can generate violent eruptions on immunocompromised subjects (such as HIV positive) and is often associated with other pathological conditions such as Parkinson’s disease, pancreatitis, hepatitis C, etc.

Seborrheic dermatitis: symptoms and risk factors

Seborrheic dermatitis is symptomatic.

While the signs of this disease are often common to other conditions, in the case of seborrheic dermatitis they usually appear gradually.

The initial onset is in fact represented simply by the presence of slightly reddened skin followed by flaking in the presence of usually yellowish and rather greasy crusts.

Added to this are also localized itching and burning and, in more rare cases, folliculitis or alopecia (if seborrheic dermatitis affects the scalp).

In this specific case, the hair is often dry, frizzy and oily.

Specialists strongly recommend that patients with seborrheic dermatitis avoid scratching as this worsens the infection, making the skin even more sensitive, irritated and red.

It has been clinically observed that the intensity of symptoms varies according to the severity of the disease. Furthermore, the irritation occurs in a more violent form in subjects with immunosuppression or neurological problems such as HIV or Parkinson’s disease.

Among other risk factors, it has been observed that oily skin favors the development of the disease.

In subjects in which the disease is more manifest, red-yellowish papules may also appear, often painful to the touch.

Seborrheic dermatitis: the causes

Although the causes that lead to the eruption of seborrheic dermatitis are not yet fully understood and vary among individuals, there are nevertheless common factors that can lead to the manifestation of the disease.

It has been scientifically proven that factors related to hormonal and endocrine activity are joined by others related to diet and familiarity.

Environmental factors such as smog, pollution and often hot and humid environments can also affect the course of the disease.

Seborrheic dermatitis is a seasonal and intermittent disease.

It usually gets worse with the cold and improves with the arrival of the summer season as it enjoys the beneficial effects of exposure to UVA rays.

Other factors that negatively affect the onset of symptoms are:

Psycho-physical stress: as with any other type of pathology, this is never beneficial and contributes to worsening symptoms.
Unbalanced diet, for example too rich in fats and sugars and with vitamin deficiencies (especially group B) and excessive alcohol intake.
Previous pathologies involving the immune or endocrine system.
Prolonged intake of certain drugs such as corticosteroids.
Too hot and humid climatic environments.
Poor hygiene or use of shampoos and soaps that are too aggressive for the skin.

Types of seborrheic dermatitis

There are clinically different types of seborrheic dermatitis, depending on the anatomical area in which it develops and the age group of the affected patient.

Usually the most affected areas remain those rich in sebaceous glands.

Seborrheic dermatitis of the face is, together with that of the scalp, the most common form.

It presents with redness and cracked skin, mainly in the furrows between the nostrils and mouth, near the eyebrows (often affected by rebound alopecia), on the eyelids, in the auditory area, on the forehead and chin.

The scalp is the area where sebum and microorganisms settle best, contributing to the proliferation of the disease.

In the latter case, the main symptom is abundant dandruff.

These two localizations affect both sexes in the same percentage, as well as the pubic localization (less frequent).

On the other hand, the localization on the sternum and under the beard predominantly affects the male sex.

Cases of neonatal seborrheic dermatitis are not uncommon.

In this specific phase of life, the symptoms with which it presents are usually red papules on the face and cradle cap on the scalp.

Even in the neonatal form we recognize the presence of lesions, dandruff and yellowish desquamation.

Chronic diaper dermatitis is also generally associated with these symptoms.

Seborrheic dermatitis: the diagnosis

The diagnosis of seborrheic dermatitis must be made only and exclusively by a dermatologist who, during the physical examination, observes and studies the signs and symptoms.

To support this, the specialist can make use of a skin biopsy, directly taking a skin sample from the lesion.

The result of the biopsy determines a very accurate and precise diagnosis.

Treatments for seborrheic dermatitis

To date, there is no definitive cure for seborrheic dermatitis.

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Topical and oral remedies with an anti-inflammatory, antifungal and sebum-regulating action are usually used for therapeutic purposes to relieve and improve symptoms and manifestations.

Among these we find:

capsules and tablets containing selenium sulfide, zinc, coal tar and ketoconazole, to be taken orally according to a doctor’s prescription. They are all antifungal drugs that counteract the proliferation of Malassezia strains.
anti-dandruff shampoos and foams and sebum regulators, specific for a scalp affected by dermatitis.
skin products also with a sebum-regulating action for other locations.
phototherapy based on UVA rays. To mimic the beneficial effects observed from sun exposure.

For all the therapies indicated above, it is always recommended to undergo a medical consultation.

Only the specialist will in fact be able to choose the most suitable solutions based on the patient’s clinic, on his response to any previous therapies and on the severity of the eczema manifestation.

Seborrheic dermatitis: a few rules to prevent it

It is possible to reduce or minimize the symptoms of seborrheic dermatitis by following a few simple prevention rules which first of all include adopting a healthy lifestyle.

Following a good diet, associated with regular physical exercise, is the basis for maintaining a body that is always fit and healthy, and a stronger immune system capable of directly fighting infections.

Adopting a diet too rich in sugars and saturated fats can worsen the course of dermatitis.

The same goes for the unregulated intake of dairy and leavened products.

Always prefer the consumption of oily fish which, rich in Omega 3, relieves inflammation and makes the immune system more reactive.

In all anatomical areas affected by seborrheic dermatitis never use irritating products.

During the bath and shower, prefer delicate soaps and shampoos based on natural ingredients, rather than very aggressive ones.

Always make sure to rinse thoroughly any residue of products used for washing.

Whenever possible, make sure to keep the affected areas in contact with cotton and breathable fabrics.

It is also recommended to avoid touching eczema continuously to avoid bacterial over-infections or mechanical irritations which would make the situation worse.

Do not wash your hair excessively as this irritates the scalp even more making it even more sensitive and prone to irritation.