Seborrhoeic Dermatitis

Seborrhoeic dermatitis is a long-term skin disorder characterised by flaky, scaly, greasy, and occasionally itchy and inflamed skin. It primarily affects areas rich in oil-producing glands such as the scalp, face, and chest, and can result in social or self-esteem problems. In infants, it is often referred to as cradle cap when the scalp is involved.

Seborrhoeic dermatitis of the scalp is sometimes described as dandruff, although not all dandruff is due to this condition.

The exact cause is unclear but is believed to involve a combination of genetic and environmental factors. Poor immune function, Parkinson's disease, and stress are notable risk factors.

Signs and Symptoms

Seborrhoeic dermatitis typically presents as dry, white, flaky skin which can be fine, loose, and diffuse or thick and adherent. Flakes can also appear yellow and greasy. In addition to flaky skin, there can be red, inflamed, and itchy skin.

The scalp, face, ears, and trunk are commonly affected, while intertriginous areas like the groin or underarm are less commonly involved. Symptoms can range from mild and persistent over weeks to severe and quick in onset, particularly in immunocompromised individuals.

Causes

The exact cause of seborrhoeic dermatitis remains unclear. Factors include genetic predisposition, environmental triggers, hormonal changes, and immune system dysfunction. The yeast Malassezia is thought to play a significant role, particularly in sebum-rich areas.

Fungi

High counts of Malassezia species are observed in affected skin, and antifungal treatments are effective, suggesting a local inflammatory response to Malassezia overgrowth.

Bacteria

Some bacteria, including Propionibacterium and Staphylococcus aureus, interact with seborrhoeic dermatitis, though their exact roles are not well understood.

Other Factors

Nutritional deficiencies, particularly in vitamin B6 and B2, immune dysfunction, particularly in HIV or neurological disorders like Parkinson's disease, and climate variations can exacerbate the condition.

Diagnosis

Diagnosis is typically clinical, based on symptoms and physical examination. Additional tests like a Wood's Lamp examination, KOH test, or fungal culture may be employed to rule out other conditions.

Differential Diagnosis

Conditions that may mimic seborrhoeic dermatitis include:

• Atopic dermatitis
• Contact dermatitis
• Psoriasis
• Tinea infections
• Candidiasis

Management

Medications

A variety of medications can reduce symptoms, including antifungals, anti-inflammatory agents, and keratolytics.

Antifungals

Topical antifungals like ketoconazole and ciclopirox are commonly used. Shampoos containing zinc pyrithione or selenium sulphide are also effective.

Anti-inflammatory Treatments

Topical corticosteroids are effective for short-term treatment but cannot be used long-term due to skin-thinning side effects. Calcineurin inhibitors like tacrolimus and pimecrolimus are alternatives.

Antihistamines

These are primarily used to reduce itching.

Keratolytics

Substances like urea, salicylic acid, and coal tar help exfoliate built-up skin flakes.

Other Treatments

• Isotretinoin for reducing sebaceous gland activity in severe cases
• Topical metronidazole, nicotinamide, and sulfacetamide
• Tea tree oil and cannabidiol shampoo

Phototherapy

Natural and artificial UV radiation can inhibit Malassezia growth and reduce inflammation.

Outcome

Seborrhoeic dermatitis is generally chronic and recurrent, with periods of relapse and remission. It affects 1 to 5% of the population, with higher incidence in males, African-Americans, and those with compromised immune systems.

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Self-assessment MCQs (single best answer)

What is Seborrhoeic dermatitis primarily characterised by?

In infants, seborrhoeic dermatitis of the scalp is often referred to as:

Which organism is believed to play a significant role in seborrhoeic dermatitis?

Which of the following is NOT a common location affected by seborrhoeic dermatitis?

Which of the following is a known risk factor for seborrhoeic dermatitis?

Which type of treatment is commonly used for seborrhoeic dermatitis due to its antifungal properties?

Topical corticosteroids are effective for short-term treatment of seborrhoeic dermatitis but cannot be used long-term due to:

Which vitamin deficiencies are associated with exacerbation of seborrhoeic dermatitis?

What is the main role of keratolytics in the management of seborrhoeic dermatitis?

Which of the following is NOT typically used to manage seborrhoeic dermatitis?