Seborrhoeic Dermatitis

Synonyms: seborrhoeic eczema

Seborrhoeic dermatitis (SD) is a common, benign skin condition which usually involves the face or scalp, though it may affect other areas. It produces a scaling rash. It can affect any age from puberty onwards. An infantile form also exists (see below).

Seborrhoeic dermatitis is probably an inflammatory reaction to a yeast called Malassezia (formerly known as Pityrosporum ovale). This yeast may be a normal skin commensal. Patients with seborrhoeic dermatitis may have a reduced resistance to the yeast.

Symptoms may be aggravated by illness, psychological stress, fatigue, change of season, poor immune function (e.g. HIV) and certain medications.³

Pityriasis capitis i.e. "dandruff", is an uninflamed form of seborrhoeic dermatitis of the scalp.

• Face and scalp:
  • SD presents as inflamed areas with fine scaling. This affected areas are the nasolabial fold, over the bridge of the nose, eyelashes/eyebrows and ear.⁵
  • Usually there is an associated fine scaling in the scalp to produce the "dandruff" (fine flaking seen in scalp and hair).
  • On the scalp, there may be ill-defined dry pink patches with yellowish or white bran-like scale. It may affect the entire scalp.
• Other areas:
  • Sternum and upper back (between the scapulae) - may have fine scaling plaques.
  • Flexures (axillae, groins and under breasts) - may have erythematous patches, papules or plaques.

• The distribution of SD is usually characteristic. Fine scaling ('dandruff') helps confirm the diagnosis.
• Psoriasis may look similar or may overlap with SD (see below).
• Rosacea on the face is not scaly, spares the nasolabial fold, and consists of papules and pustules on an erythematous base situated on cheeks, chin, tip of nose and forehead.

The basis of treatment is regular antifungal medication with intermittent topical steroids.

Scalp

• Medicated shampoos containing ketoconazole, selenium sulfide, zinc pyrithione, coal tar or salicylic acid. An antifungal agent is particularly useful. They are used twice a week for at least a month, after which the frequency may be reduced.
• Steroid scalp applications reduce itching. Intermittent use for a few consecutive days may be helpful (avoid continuous use).
• For scaling, coal tar cream can be applied to the scaling areas, left on for several hours and then removed by shampooing.

Face, ears, chest and back

• Keep the skin clean but avoid soap.
• Ketoconazole or another antifungal cream may be used once daily for 2 to 4 weeks. This can be repeated as necessary.
• 1% Hydrocortisone cream can be applied once or twice daily for a week or two. Again, intermittent courses may be required for this chronic condition (and continuous use or high doses should be avoided).

Other treatments

More severe SD may merit:⁴

• Oral antifungal medication - azoles (e.g. ketoconazole or itraconazole) or others e.g terbinafine.⁷
• Ultraviolet light treatment.

Other possible treatments are:

• Azelaic acid (e.g. 15% gel), which has various useful properties - antifungal, antikeratinizing, and anti-inflammatory activity.⁸
• Natural substances such as tea tree oil (Melaleuca oil), honey, and cinnamic acid have antifungal activity against Malassezia species and could be beneficial for SD.⁷
• New formulations of topical ketoconazole, e.g. gel or foam preparations.⁹
• Metronidazole gel.¹⁰
• Immunomodulators e.g. topical tacrolimus or pimecrolimus.⁸

• Secondary bacterial infection can occur.
• Severe SD or generalised seborrheic erythroderma are rare - they may occur with immunosuppression (including HIV) or cardiac failure.

The condition usually responds well to treatment. It often relapses, so maintenance or intermittent treatment may be required.

Infantile seborrheic dermatitis

Presentation:

• Affects babies up to the age of six months.
• 'Cradle cap' is the usual symptom (flaky, greasy-looking scalp).
• May also affect skin creases - axillae, groin or resembling napkin dermatitis.
• In severe cases, patches may appear on the face, trunk and limbs. These are salmon-pink, flaky and not itchy.

Management:

• Usually no treatment needed, or simple emollients.
• Hydrocortisone cream and/or topical ketoconazole may be used.
• Usually resolves by the age of one year.

Sebopsoriasis

In some cases, SD may resemble psoriasis and this 'overlap condition' may be diagnosed.