What is it
Seborrheic dermatitis (also called seborrheic eczema) is a chronic relapsing inflammatory disease of the skin closely dependent on an alteration in sebum production, which increases, causing the skin to become inflamed and causing the appearance of yellowish greasy scales on its surface (seborrhea).
As a result, the manifestations of the disorder mainly affect the skin areas richest in sebaceous glands, such as scalp, forehead, nose, chin, ears, upper trunk (especially in men, less so in women) and body folds.
More precisely, the areas affected more or less frequently by seborrheic dermatitis are:
| Most common locations | Less common locations |
|---|---|
| Scalp
Eyebrows Central area of the face (especially at the forehead, sides of the nose and chin) Folds behind the auricles and the external ear canal |
Chest (particularly in men)
Armpits Inguinal folds Intergluteal fold Mammary areolas Anogenital region |
Seborrheic dermatitis is widespread in the general world population with a prevalence of 3-5%, without significant differences between geographical areas and various ethnicities. The classical form of the disease affects adolescents and young male adults with much higher frequency and with more pronounced clinical expression, with a peak of onset typically between 20 and 40 years, when the sebaceous glands reach the maximum level of activity.
In older people, the disease occurs more often in association with neurological disorders (in particular, Parkinson’s disease): in these cases, as well as in patients with HIV/AIDS, seborrheic dermatitis tends to occur even in a more severe form.
The disorder almost never affects children under 10-12 years, while it can occur in newborns in the form of “cradle cap”: a childhood seborrheic dermatitis localized to the scalp, which affects a high percentage of newborns in the first weeks of life and regresses spontaneously by the third month.
Cradle cap, in reality, is a particular form of seborrheic dermatitis, considered not completely superimposable from the etiopathogenetic point of view to that of adults; Often, it is the first expression of an atopy condition, indicative of an increased risk of developing atopic dermatitis and allergies of various types in the following years.
Causes
Although the disease is widespread and known for a long time, it is still unclear what its primary cause is. The onset of skin manifestations is certainly conditioned by numerous factors: anatomical, biochemical, immunological, hormonal, infectious, neuropsychological, environmental and climatic.
Among the favorable conditions are: alterations of the chemical-physical characteristics of the cutaneous hydrolipidic film, impairment of the immune system, hormonal imbalances, nutritional deficiencies, psychophysical stress (including that related to acute diseases or surgery), exposure to air pollution, low temperatures and high levels of ambient humidity.
These elements and other triggers presumably contribute to induce and maintain the increased inflammatory state of the skin typical of the disease, probably also on the basis of a genetic predisposition not yet precisely determined.
The mechanism underlying the inflammatory process in the affected skin areas is an increase in sebaceous secretion, sometimes accompanied by an alteration of the characteristics of the sebum itself. This phenomenon, in turn, favors the proliferation of one of the main microorganisms of the cutaneous microbial flora, the fungus Malassezia furfur (formerly called Pityrosporum ovale), also involved in the development of pityriasis versicolor (cutaneous mycosis characterized by the appearance of coffee-milk patches on light skin or light areas on tanned skin).
The hyperactivity of the sebaceous glands, combined with the abnormal microbial growth, determine an acceleration of the natural renewal of the superficial layers of the epidermis (stratum corneum), with consequent massive desquamation of dead cells (corneocytic) and appearance of yellowish and greasy scales on areas of reddened skin or dandruff on the scalp with dermatitis.
Seborrheic dermatitis is not, however, indicative of poor hygiene: indeed, often, it is precisely too frequent washing or with aggressive detergents to sensitize the skin and to stress the activity of the sebaceous glands in an abnormal way, favoring the onset of the disorder or worsening its manifestations.
Symptoms
Adult seborrheic dermatitis is an erythematous-desquamative form. In the affected areas, redness in patches is observed, with generally sharp limits and covered by scales. The scaly formations, more or less abundant, can be dry, white or grayish, small and more or less adherent to the skin (as in the case of dandruff), or oily, yellowish, larger and raised than the skin surface (as in the case of cradle cap).
The main, and almost only, symptom of seborrheic dermatitis is itching, of varying intensity from mild to difficult to bear, and can be at the origin of the typical scratching complications, such as aggravation of inflammation and skin irritation, development of lesions and crusts, onset of bacterial or fungal infections in the affected areas.
In the localization of the chest, the disease can present with very variable clinical pictures, in which erythematous component (inflammation, irritation and redness) and desquamation can prevail over each other. In the localization to the scalp, due to the effect of excess sebum and inflammation of the hair follicles, there may be an increased loss of hair, also promoted by an accentuated propensity to rubbing due to itching from more or less intense desquamation.
Seborrheic dermatitis has a chronic-relapsing evolution, characterized by phases of remission and phases of exacerbation. Exacerbations can have a seasonal pattern, with a sharp worsening of symptoms in the cold months and a tendency to improve in spring and summer. Seasonal changes can also be triggers, as they are generally associated with changes in hormonal balance.
In the infantile form, possibly supported by different mechanisms, the classic “cradle cap” of the scalp and face is characterized by large more or less reddened patches covered by fatty desquamation, in the absence of itching.
In some cases, seborrheic dermatitis can occur in association with other dermatological diseases or in conjunction with systemic diseases, immune system disorders or medications.
Diagnosis
Usually, seborrheic dermatitis is diagnosed on the sole basis of clinical signs and symptoms, which are quite typical, without the need to undergo laboratory analysis or instrumental examinations.
However, since both in the adult and in the infantile form, the disease can take on connotations similar to those of other dermatological diseases, with which it can therefore be confused, before embarking on any treatment it is essential to contact the doctor for a competent evaluation and the prescription of the most suitable drugs for the individual case.
The main dermatological diseases that can divert the diagnosis of seborrheic dermatitis in adults are:
- rosacea (especially, when manifestations are localized on the nose and central part of the cheeks)
- psoriasis (in particular, for seborrheic dermatitis with reddened patches, dry skin and greyish-white scales)
- contact dermatitis (for example, allergic or irritative forms that can affect the scalp of those who use dyes or bleaching products)
- atopic dermatitis (especially in children-adolescents, who suffer from it much more often than adults)
- skin mycoses (in particular, when areas of reddened and scaly skin appear in the furrows and body folds, typical sites of tinea cruris, or when lesions inflamed with yellowish scales appear on the scalp, in analogy to tinea capitis).
When the family doctor also encounters a diagnostic doubt, it is necessary to undergo a dermatological examination and the appropriate specialist examinations (where applicable).
Treatment
In view of the mechanisms underlying its manifestations, the treatment of choice for the treatment of seborrheic dermatitis is the local one, aimed at four main objectives:
- removal of excess sebum at the affected sites
- the reduction of colonization by Malassezia furfur
- control of the inflammatory skin reaction
- the alleviation of discomfort, burning, pain and itching at the level of the lesions.
For this purpose, medicated shampoos, lotions and cream formulations have long been used, containing active ingredients with antifungal, keratolytic, immunomodulatory, antibacterial (zinc-pyrithione), anti-inflammatory (corticosteroids, etc.) action.
Of more recent introduction is a natural multifunctional preparation, called Alukina, consisting of the association of rock alum (mineral compound), glycyrrhetinic acid (active ingredient extract of licorice) and retinyl palmitate (an analogue of vitamin A). This combined formulation is available in the form of cream, lotion and shampoo to be able to adapt to the treatment of all areas of the body potentially affected by seborrheic dermatitis.
Among the natural substances that can assist the treatment of seborrheic dermatitis, extracts of aloe vera, Echinacea purpurea, Hypericum perforatum have proved useful. Products to be applied topically containing these phytocomplexes may offer some relief in mild forms, but alone they are not enough to reverse the acute phases of the disease.
Systemic therapies (based, for example, on antifungals or oral corticosteroids) are not normally used, as they are indicated exclusively in the rare acute and severe forms, in cases with widespread manifestations and in forms with a chronic tendency or that do not derive any benefit from local treatments.
Whatever the approach indicated by the doctor, it is important to remember that the skin and scalp with seborrheic dermatitis must also be subjected to regular cleansing, very delicate, but able to remove excess debris (such as skin scales and superficial scabs already in the detachment phase) and residues of topical preparations used previously, before each new application. In order not to risk sensitizing the already strongly destabilized and inflamed skin, it is good to seek advice from the dermatologist specific cleansing products, taking into account the area of the body affected by the lesions.
For seborrheic dermatitis localized in skin areas without or with modest hair, after each wash and before the application of specific topical drugs, it may be useful to apply a high quality moisturizer, formulated for sensitized skin. This precaution is important especially in the presence of dry skin, because it helps to promote the absorption of the active ingredients applied subsequently and to improve the restoration of the physiological skin barrier.
During the treatment of the scalp with seborrheic dermatitis it is important to suspend the use of any non-essential cosmetic products (such as dyes, bleaching lotions, gels, lacquers, hair masks, etc.) in order not to further stress the inflamed scalp and to avoid unfavorable interactions with drugs and related adverse events.
Joycelyn Elders is the author and creator of EmpowerEssence, a health and wellness blog. Elders is a respected public health advocate and pediatrician dedicated to promoting general health and well-being.
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