seborrheic dermatitis

Seborrheic dermatitis is an inflammatory condition that has been speculated to be caused by Malassezia yeasts. This impacts the scalp, hairline, and face that produces itchiness, dandruff and greasing on the skin. This is a harmless condition that can be treated easily.

Epidemiology

3-5% globally is the prevalence rate of seborrheic dermatitis
In the US, 300 million dollars are spent yearly on over-the-counter treatment for dandruff [1]
Affects up to 5 in every 100 adults according to Bupa UK
50% of adults have dandruff (a mild form of sebrayorrhoeic dermatitis)
Men are more likely than women to get the condition [2]

Source: DermNetNZ.org

Seborrheic dermatitis
Hypo-pigmentation (low levels of pigment) in the skin with an HIV patient

Source: DermNetNZ.org

Seborrheic dermatitis
Close up image of yellow greasy scales found on the scalp of someone with seborrheic dermatitis

Causes [3]
- Caused by a combination of genetic and environmental factors
- The Malassezia yeast overgrows and the immune system overreacts to the yeast
- Triggers include:
  - Stress
  - Hormonal changes
  - Harsh chemicals/soaps/detergents
  - Environmental changes (eg. cold, dry)
  - Medications such as lithium
- Underlying conditions such as HIV and Parkinson’s

Pathophysiology [4]
- Medical students
  - Seborrheic dermatitis (SD) is a common papulosquamous condition with similarities to psoriasis.
    - Clinically, it may be associated with excessive oiliness (seborrhea) and dandruff.
    - The condition can manifest as yellowish, dry, or greasy scales and erythmatous, follicular, scaly papules (spots) that may form large plaques or circinate patches (patches affected)
  - SD can occur in infancy (typically between 2 and 12 weeks of age) or in middle-aged and elderly individuals, and it tends to recur throughout life.
  - The exact cause of SD is poorly understood, but both environmental and intrinsic factors play a role.
  - Genes related to the immune response and epidermal differentiation are implicated in SD etiology.
  - Malassezia yeast organisms are not the primary cause, but they may act in conjunction with depressed helper T cells (SD is common in AIDS).
  - Other contributing factors include increased natural killer cells, elevated inflammatory cytokines, higher sebum levels, activation of the alternate complement pathway, and genetic susceptibility to skin-barrier dysfunction.
  - Malassezia species have lipase activity, which releases inflammatory arachidonic acid, potentially aggravating SD.
  - SD can be worsened by factors such as changes in humidity, scratching, emotional stress, diet, certain medications, and androgen excess.
- Patients
  - Seborrheic dermatitis (SD) is a common condition with similarities to psoriasis.
    - Clinically, it may be associated with excessive oiliness (seborrhoea) and dandruff.
    - The condition can manifest as yellowish, dry, or greasy scales and redness, follicular, scaly papules that may form large plaques or circinate patches.
  - SD can occur in infancy (typically between 2 and 12 weeks of age) or in middle-aged and elderly individuals, and it tends to recur throughout life.
  - The exact cause of SD is poorly understood, but both environmental and intrinsic factors play a role.
  - Genes related to the immune response and skin changes are implicated in SD
  - Malassezia yeast organisms are not the primary cause, but they may act in conjunction with cells involved in the immune response
  - Other contributing factors include increased immune cells, inflammatory proteins, and genetics increasing the likelihood of skin-barrier dysfunction.
  - Malassezia species contribute to inflammatory arachidonic acid (involved in the immune response) release potentially aggravating SD.
  - SD can be worsened by factors such as changes in humidity, scratching, emotional stress, diet, certain medications, and androgen excess.

Seborrheic dermatitis

The beard area is a typical region for seborrheic dermatitis with redness and dry skin

Risk factors [5]
- Male
- Increased sebacous gland activity
- Weakened immune system such as HIV and lymphoma
- Neurological diseases such as stroke, and parkinsons disease
- Drug usage such as;
- Lithium
- Immune suppressants
- Dopamine antagonists
- Environmental changes with low humidity and cold temperatures
Presentation [6]
- Dry flakey skin
- Greasy scaling on the scalp
- Redness and scaling on regions of the skin such as the back of the ear, eyebrows and along the hairline
- Thick, stuck-on scaly plaques on the scalp
Investigations [7]
- Clinical assessment of the appearance and a history of symptoms
- Skin biopsy may be needed to investigate the skin under the microscope to rule out infections

Seborrheic dermatitis

Faint redness and scaling along the creases of the nose seen on darker skin tones

Differential diagnosis [8]
- Psoriasis
- Atopic dermatitis/ allergic contact dermatitis- inflammation of the skin caused by allergens
- Tinea capitis- ringworm
- Rosacea- redness of the skin
- Systemic lupus erythematous- butterfly rash on the face

Source: DermNetNZ.org

Seborrheic dermatitis
Pigmented seborrheic dermatitis found around the nose and under the eyes

Source: DermNetNZ.org

Seborrheic dermatitis
Scaling and dryness around the hair line and forehead

Management [9]
- Medical Students and Patients
  - Scalp and beard
    - Seborrhoeic dermatitis in adults is a chronic condition, and long-term maintenance treatment may be necessary.
      - Advise avoiding soap and shaving cream on the face if they cause irritation and instead use non-greasy emollient soap substitutes.
      - Stress may exacerbate seborrhoeic dermatitis and lead to flares.
    - Treat seborrhoeic dermatitis of the scalp and beard in adolescents and adults with ketoconazole shampoo
      - Scales can be removed before shampooing by applying warm mineral or olive oil (for mild crusting) or a keratolytic preparation (such as salicylic acid and coconut oil for thicker scale) for several hours before shampooing.
      - Leave the shampoo on for 5 minutes before rinsing off.
      - Other medicated shampoos like zinc pyrithione, coal tar, or salicylic acid can be used if ketoconazole is not suitable.
    - For severe itching of the scalp, consider co-prescribing a short course of a topical corticosteroid scalp application like betamethasone valerate or mometasone furoate
    - Topical corticosteroids are not suitable for application to the beard due to adverse effects on the face's skin.
    - Routine follow-up is not usually required, but review should be done if response to treatment is poor, symptoms worsen, or signs of infection develop.
    - Consider referral to a dermatologist in cases of diagnostic uncertainty, treatment failure, or severe or widespread seborrhoeic dermatitis.
  - Face and body
    - Seborrhoeic dermatitis in adults is a chronic condition, and long-term maintenance treatment may be necessary.
    - Advise avoiding soap and shaving cream on the face if they cause irritation, and use non-greasy emollients or emollient soap substitutes.
    - Stress may exacerbate seborrhoeic dermatitis and lead to flares.
    - Treat seborrhoeic dermatitis of the face and body in adults with ketoconazole cream or another imidazole cream (clotrimazole or miconazole) for at least 4 weeks. An antifungal shampoo like ketoconazole can be used as a body wash.
    - Once symptoms are under control, ketoconazole cream can be used less frequently to prevent recurrence.
    - Consider using mildly potent topical corticosteroids like hydrocortisone or hydrocortisone for flares to help settle inflammation.
      - Use these corticosteroids short-term to minimise adverse effects.
      - For children and adolescents, treat seborrhoeic dermatitis with imidazole cream (clotrimazole or miconazole).
      - Mild topical corticosteroids like hydrocortisone or hydrocortisone can be added for flares, but use them for one week only to avoid adverse effects.
    - In adolescents, an antifungal shampoo like ketoconazole (not for children under 12) may be used as a body wash. Shampoo should be left on for 5 minutes before rinsing off.
    - If the eyelids are involved, daily hygiene measures using cotton buds moistened with baby shampoo can be helpful.
    - Routine follow-up is usually not required, but review is advised if treatment response is poor, symptoms worsen, or signs of infection develop.
    - Consider referral to a dermatologist or paediatrician for diagnostic uncertainty, treatment failure, severe or widespread seborrhoeic dermatitis, or eyelid involvement that does not respond to hygiene measures.
Complications
- Areas exposed to moisture and eyelids are prone to secondary infections
- In infants, the diaper area commonly growth the fungal infection
- Self esteem- self worth complications from appearance
- Skin thinning and dilated blood vessels [10,11]

Seborrheic Dermatitis

Seborrheic dermatitis found behind the fold of the ear in a grey, linear spread on brown skin

Seborrheic Dermatitis

Often affects the chest in men with redness, scaling and round patches under the breasts and along the breastbone

Myths about dandruff [12]
- You should remove the dry flakes before shampooing the hair
- Dandruff is worse in the summer
- All flakes are a sign of dandruff
- Seborrheic dermatitis is the cause of all dandruff
Questions to ask your doctor
- What causes seborrheic dermatitis?
- How can you diagnose the cause of my dandruff?
- How long will treatment take to be effective?
- What lifestyle changes can I make to manage my symptoms?
- If I take other medications, will that change my treatment plan for my seborrheic dermatitis?
Support
- Bupa UK
- National Eczema Society
- American Academy of Dermatology