Due to progressive developments in their nomenclature, there is some confusion about the classification and naming convention of Malassezia yeast species. Work on these yeasts has been challenging and more complicated due to the requirement of specific growth media, and it tends to grow very slowly in laboratory culture.
The French scientist Louis-Charles Malassez initially identified Malassezia in the late 19th century. Raymond Sabouraud distinguished a dandruff-causing organism in 1904 and named it “Pityrosporum malassez,” honoring Malassez, but at the species level as rather than at the genus level. When it was discovered that the organisms were the same, the term “Malassezia” was found to hold priority.
In the mid-20th century, it was reclassified into two species:
Pityrosporum (Malassezia) ovale, are lipid-dependent and observed only on humans. P. ovale was later split into two species, P. ovale and P. orbiculare, but current references consider these terms to apply to a single species of fungus, with M. furfur the chosen name.
Pityrosporum (Malassezia) pachydermatis, which is lipophilic however it’s not lipid-dependent, is found on the skin of most animals.
In the mid-1990s, scientists at the Pasteur Institute in Paris, France, discovered new species.
Currently, there are at least 14 recognized species:
Role in human diseases
Identification of Malassezia on skin has been aided by the application of molecular or DNA-based techniques. These studies show that the Malassezia species are causing most skin disease in humans, including the most frequent cause of seborrhoeic dermatitis and dandruff, is M. globosa (though M. restricta is also involved). The skin rash of tinea versicolor (pityriasis versicolor) is also due to infection by this fungus.
Since the fungus needs fat to grow, it is most prevalent in areas with many sebaceous glands: on the face, scalp, and upper portion of the body. When the fungus proliferates, the natural renewal of cells is disturbed, and dandruff follows with itching (a comparable outcome may also occur with other fungi or bacteria).
A project in 2007 has sequenced the genome of dandruff-causing Malassezia globosa and found it to have 4,285 genes.M. globosa uses eight separate kinds of lipase, along with three phospholipases, to understand the oils within the scalp. Any of these 11 proteins would be a proper target for dandruff medications.
M. globosa has been envisioned to have the ability to reproduce sexually, but this has not been observed.
Treatment of symptomatic scalp infections
Symptomatic scalp infections are often addressed with zinc pyrithione selenium disulfide, or ketoconazole containing shampoos.
There are several natural antifungal treatments for seborrhoeic dermatitis including garlic, onions, apple cider vinegar, coconut oil, tea tree oil (Melaleuca alternifolia oil), honey, and Cinnamic acid
Some medications can manage seborrhoeic dermatitis including certain antifungals, topical corticosteroids, and keratolytic such as topical urea, as well as antihistamines and antiandrogens antihistamines.
Daily use of a prescription or over-the-counter anti-fungal shampoo can assist people with recurrent episodes. The topical antifungal medications ketoconazole and ciclopirox have the best evidence. It is not for certain if other antifungals have equal effectiveness as this has not been studied. Another potential option is natural and synthetic UV radiation since it can curb the germination of Malassezia yeast.
Seborrhoea is understood as an androgen-sensitive condition – that is, it is produced or exacerbated by androgen sex hormones such as dihydrotestosterone and testosterone a– and is a common symptom of hyperandrogenism (e.g., that observed in polycystic ovary syndrome). Also, acne, as well as seborrhoea, are commonly linked with puberty due to the steep increase of androgen levels at that time.
Per the involvement of androgens in seborrhoea, antiandrogens, such as cyproterone acetate, spironolactone, and flutamide, are highly effective in alleviating the condition. As such, they are utilized in the treatment of seborrhoea, particularly in severe cases. While beneficial in seborrhoea, effectiveness may vary with different antiandrogens; for instance, spironolactone (which is regarded as a relatively weak antiandrogen) has been found to produce a 50% improvement after three months of treatment, whereas flutamide has been found to result in an 80% improvement within three months. Cyproterone acetate is similarly more potent and effective than spironolactone and results in considerable improvement or disappearance of acne and seborrhoea in 90% of patients within three months.
Systemic antiandrogen therapy should exclusively be employed to treat seborrhoea in women, and never in men, as these medications can result in sexual dysfunction, feminization (e.g., gynecomastia), and infertility in males. Besides, antiandrogens have the potential to feminize male fetuses in pregnant women, and for this reason, should always be coupled with effective contraception in sexually active women who can or may become pregnant.
Antihistamines are used principally to decrease itching if present. However, research studies insinuate that some antihistamines have anti-inflammatory characteristics.
Topical steroids have been proved to be effective in short-term treatment of seborrhoeic dermatitis and are as effective or more effective than azole treatment. There is also proof for the effectiveness of calcineurin inhibitors and lithium salt treatment.
Coal tar can be effective, but, although no significant increased risk of cancer in human treatment with coal tar shampoos has been found, caution is advised since coal tar is carcinogenic in animals, and heavy human occupational exposures do increase cancer risks.
Pimecrolimus topical cream immunosuppressant
Prednisone — an oral immunosuppressive treatment that has been used in short courses as a last resort due to its potential side effects.
Isotretinoin — As the last option in refractory disease, sebosuppressive agent isotretinoin may be used to decrease sebaceous gland activity. However, isotretinoin possibly has dangerous side effects, and few patients with seborrhoea are suitable candidates for therapy.
Some recommend photodynamic therapy using UV-A, and UV-B laser or red and blue LED light to inhibit the growth of Malassezia fungus and reduce seborrhoeic inflammation.