Seborrheic Dermatitis

Seborrheic dermatitis is a chronic, relapsing inflammatory skin condition related to the body's immune response to Malassezia yeast, which thrives in sebum-rich environments.

• Symptoms: Patients report persistent flaking and itching (pruritus). The itch is typically mild to moderate but chronic.

• Distribution: The "sebaceous" areas are key. Patients will note patches on the scalp (dandruff), eyebrows, sides of the nose (nasolabial folds), and the center of the chest.

• Triggers: They often report that the condition flares during cold, dry weather or during periods of high emotional stress.

• Course: It is a relapsing-remitting condition. Patients often describe it as something that "comes and goes" for years.

• Medical History: SD is notably more severe in patients with Parkinson’s disease or HIV/AIDS, where it may be the presenting sign of immunosuppression.

The diagnosis is clinical, centered on the location and the "greasy" quality of the scales.

• Morphology: Erythematous (red), ill-defined patches covered with greasy, yellowish, or "bran-like" scales.

• Distribution (Sebaceous Areas):

  • Scalp: Ranges from fine white flaking (pityriasis sicca) to thick, adherent crusts.

  • Face: Characteristically involves the medial eyebrows, glabella (between the eyes), and nasolabial folds.

  • Trunk: Often presents as a "petaloid" (flower-shaped) or annular pattern over the sternum.

  • Flexural: In the armpits or under the breasts, it may lack the classic scale and appear as "Inverse SD"—shiny, red, and well-demarcated.

Crucial Note for Darker Skin Tones

• Hypopigmentation: In Black skin, SD frequently presents as hypopigmented (pale) patches with very little redness. This is often mistaken for Pityriasis Alba or Vitiligo.

• Color of Scale: The scale may appear white, grayish, or yellowish, which creates a high contrast against pigmented skin.

• Petaloid Pattern: This variant is particularly common in skin of color, appearing as circular or "flower-petal" shaped rings on the face and chest.

• Hair Practices: In patients who wash their hair less frequently due to hair texture (e.g., tightly coiled hair), the scalp scale may become very thick and lead to seborrheic alopecia (temporary hair thinning due to inflammation).

• Differential Diagnosis:

  • Scalp Psoriasis: Scales are typically "silvery," thicker, and the patches are very well-demarcated, often extending beyond the hairline.

  • Tinea Capitis: Always rule out fungal ringworm in children with a scaly scalp, especially if there is associated hair loss or lymphadenopathy.

Since SD is chronic, the goal is "clearance and maintenance" rather than a permanent cure.

1. Antifungal Therapy (Targeting Malassezia):

   • Topical Creams: Ketoconazole 2% cream or Ciclopirox 0.77% gel. Apply once or twice daily for 2–4 weeks until clear.

   • Medicated Shampoos: 

     • Ketoconazole 2% shampoo (Nizoral).

     • Selenium sulfide 2.5% suspension (Selsun).

     • Protocol: Apply to the scalp (and beard/chest if needed), lather, and leave for 5–10 minutes before rinsing. Use twice weekly for treatment, then once weekly for maintenance.

2. Anti-Inflammatory Therapy (For Flares):

   • Topical Steroids: For severe redness or itching, use low-potency steroids like Hydrocortisone 1% cream on the face twice daily for no more than 1–2 weeks.

   • Potency Caution: Avoid high-potency steroids on the face to prevent thinning (atrophy) and perioral dermatitis.

   • Topical Calneurin Inhibitors (TCI): Tacrolimus 0.1% ointment or Pimecrolimus 1% cream are excellent "steroid-free" alternatives for long-term facial maintenance.

3. Keratolytics (For Thick Scale):

   • Shampoos containing Salicylic acid or Coal tar help break down thick "cradle cap" or scalp crusts so that the antifungal can reach the skin.

4. Maintenance Protocol:

   • Once clear, advise the patient to use their medicated shampoo (e.g., Selenium sulfide) once every 1–2 weeks indefinitely to prevent the yeast population from rebounding.

Darker Skin Tones – Specific Treatment Risks:

• Pigment Recovery: Reassure the patient that the hypopigmented (pale) spots are not permanent scars. Once the inflammation is controlled with antifungals, the color will naturally return over several months.

• Moisture Balance: Many medicated shampoos can be very drying to coiled or "Type 4" hair. Advise the patient to apply the shampoo only to the scalp and use a deep conditioner on the hair shafts afterward to prevent breakage.

• DermNet NZ – Seborrheic Dermatitis: https://dermnetnz.org/topics/seborrhoeic-dermatitis

• StatPearls – Seborrheic Dermatitis (2024 update): https://www.ncbi.nlm.nih.gov/books/NBK531483/

• American Family Physician – Diagnosis and Treatment of Seborrheic Dermatitis.