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Malassezia Infections of the Skin

D. R. Thomas, MD, FRCPC
Department of Dermatology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada

The Organism

Malassezia are lipophilic yeasts that are normal commensals on the skin surface. Named after French microbiologist Louis Charles Malassez (1842-1909), there are seven species of these yeasts, which were previously called Pityrosporum. They usually form colonies in the skin in late childhood and adult life, but can be found in some neonates. The conditions described in this article are either caused by the Malassezia itself or from some kind of immunological or toxic reaction to the organism.

Malassezia can cause:

  • Dandruff
  • Adult seborrheic dermatitis
  • Pityriasis versicolor
  • Pityrosporum (Malassezia) folliculitis

The treatment recommendations are based on evidence-based medicine, physician experience, and patient preference.

Dandruff

What It Is
  • Also known as pityriasis capitis. Caused by M. globosa which produces oleic acid from its action on sebum, it is an irritant to skin.
  • This is the mild end of the spectrum of seborrheic dermatitis. It is very common, with white scaling on the scalp but no inflammatory reaction, as seen in true seborrheic dermatitis.
Treatment
  • Shampoos active against Malassezia yeasts are usually sufficient for this condition. These shampoos can be either antifungal, keratolytic (salicylic acid), or cytostatic (coal tar). They can be used daily until control is achieved, and then the frequency can be reduced to prn (often 1-3 times a week).
Antiyeast shampoos
  • Over-the-counter (OTC)
    • Zinc pyrithione (Head & Shoulders®) Zinc pyrithione shampoos have been developed in recent years to ensure that particle size, shape, and adherence of the therapeutic molecule give improved bioavailability, and therefore greater effectiveness. Cosmetically elegant shampoos are now produced with great acceptance by consumers.
    • Selenium sulfide (Selsun®) – very actively antifungal
    • Ketoconazole (Nizoral®)
  • Prescription
    • Ciclopirox shampoo (Loprox®)

Seborrheic Dermatitis

What It Is
  • A common (5% prevalence) chronic relapsing rash seen in adults Quite well-defined erythematous lesions that do not cross the hair line of the scalp
  • Accompanied by a greasy looking scale
  • Located on the scalp, medial eyebrows, in and around the ears, central chest, and upper back. It may also be found in the intertriginous areas. Rarely, it is generalized.
  • More extensive and inflammatory variants are seen in patients with AIDS.
Risk Factors
  • Neurological conditions, e.g., poststroke, Parkinsonism
  • HIV-AIDS
  • Antipsychotic drugs
Differential Diagnosis
  • Scalp:
    • Scalp Psoriasis
      • Well-defined lesions that may extend beyond the hairline. The scale is more silvery than the greasy yellowish-brown colour seen in seborrheic dermatitis. May have involvement in other typical sites. Central facial involvement uncommon. It may sometimes be impossible to distinguish the two conditions.
    • Tinea Capitis
      • Usually seen in children. There is a spectrum of appearance ranging from mild scaling to boggy plaques.
    • Atopic Dermatitis
      • May be aggravated on the face, neck, and upper chest by Malassezia yeast.
  • Face:
    • Facial Rosacea
      • Central face with papules and pustules. Flushing always present. Nasolabial and paranasal scale not usually present but blepharitis is seen in both. The two conditions quite frequently coexist. Systemic lupus does not exhibit papules and pustules.
    • Intertriginous Seborrheic Dermatitis
      • Erythrasma, intertrigo, psoriasis
Treatment
  • The selection of therapy depends on the effectiveness, ease of use, and cosmetic acceptability of the products. The face, scalp, and chest are the most common sites of involvement.
Evidence-Based Therapy
  • Evidence-Based Therapy
  • Oral and topical ketoconazole, and hydrocortisone are first-line treatments.
  • Lithium succinate ointment, 15% propylene glycol in water.
  • Zinc pyrithione shampoo (Head & Shoulders®)
Suggested Therapy
  • Gain control of facial dermatitis with topical ketoconazole cream. Hydrocortisone 1% cream can be added if necessary.
  • OTC: Antiyeast shampoos, e.g., zinc pyrithione (Head & Shoulders®) can be used in the shower, first on the scalp in the usual way, and then rubbing the lather onto the face and chest if necessary and left on for 30-60 seconds before washing off. If this is not effective, other antiyeast shampoos can be tried in a similar fashion. Patients often prefer treating this condition in the shower rather than by applying creams.
  • If the scalp is unresponsive to topical steroid solutions, gels and shampoos can be used on the scalp (e.g., betamethasone valerate solutions [e.g., Betnovate®] flucinonide gels, clobetasone shampoo [Clobex®]).
  • The use of immunomodulators such as pimecrolimus cream (Elidel®) has been found to be helpful for the control of facial seborrheic dermatitis that is unresponsive to other therapy. Tacrolimus ointment (Protopic®) has also been found to be helpful.

Pityriasis Versicolor

What It Is
  • Infection confined to the trunk and proximal limbs when the yeast transforms into hyphae. Hair and nails are never involved.
  • Fine scaly patches of varying color, red, brown, and white; usually in young adults. Seen on the upper trunk, neck, upper arms, and occasionally the scalp.
  • Hypopigmented patches, caused by the yeast, produce azelaic acid, which inhibits melanin production. The hypopigmentation may last for months after the yeast overgrowth has been controlled. Occasionally the condition remits spontaneously.
  • The diagnosis is confirmed by the appearance of spores and hyphae (spaghetti and meatballs) on KOH exam of skin scrapings of the scale.
Risk Factors
  • Sun exposure
  • Pregnancy
  • Sweating
  • Cushing’s syndrome
  • Interestingly, it is not more common in HIV-AIDS
Differential Diagnosis
  • Vitiligo is commonly seen on the face, hands and genitals. There is no scale present. Much more complete depigmentation. Frequent hyperpigmentation at the edges of the lesions, which often vary in size. Depigmentation of hair can occur.
  • Other conditions to consider are tinea corporis and postinflammatory hypopigmentation.
Treatment
  • The erythematous and brown patches tend to respond quickly to therapy.
  • Hypopigmented lesions are slow to respond, persisting long after the yeast infection has cleared. Sun exposure may be required to stimulate repigmentation.
  • High recurrence rate, especially for those who exercise and sweat regularly. Maintenance treatment is often required, especially in the summer months.
Evidence-Based Therapy
  • Topical antifungal creams, i.e., ketoconazole, clotrimazole, and terbinafine have been shown to be effective. Ketoconazole shampoo is also effective.
  • Oral itraconazole (200mg daily for 1 week), ketoconazole (400mg single dose, repeated in 1 week) and fluconazole (Diflucan®) (150mg-300mg weekly for 1 month) have been shown to be effective.
  • Propylene glycol 50% in water b.i.d. for 2 weeks.
  • 1% zinc pyrithione shampoo applied in the shower and left on for 5 minutes.
  • Selenium sulfide 2.5% lotion daily and left on for 10 minutes for 1 week.
  • A combination of honey, olive oil, and beeswax in equal parts used t.i.d. has been shown to be effective.
Suggested Therapy
  • Patients can be given a choice of oral or topical therapy. The surface areas are large, making the application of antifungal creams difficult and costly.
  • Most will clear with the OTC shampoos such as zinc pyrithione or ketoconazole applied in the shower and left on for a few minutes before being washed off.
  • Selenium sulfide shampoos can be irritating.
  • Those with very extensive or resistant involvement can opt for systemic therapy. It must be noted that oral terbinafine is ineffective for this condition. A short course of ketoconazole or fluconazole can be used at the doses shown above. Oral ketoconazole can be hepatotoxic, but is not thought a problem for such short courses.

Pitysporum (Malassezia) Folliculitis

Seen in Three Scenarios
  • Back and upper chest involved with itchy papules and pustules.
  • Associated with seborrheic dermatitis on the upper trunk.
  • Multiple pustules on the face and trunk in HIV+ individuals
Treatment
  • Treat the underlying condition.
  • Topical antiyeast creams are recommended.
  • If no response to oral antifungals, treat as discussed for pityriasis versicolor.