Malassezia yeasts are found on the skin flora of humans and some warm-blooded animals. They feed mainly on long-chain fatty acids. The only exception here is the species M. Pachydermatis.
Due to the necessary supply of long-chain fatty acids, Malassezia yeasts are very frequently found in sebum-rich regions of the skin.
Examples are
- scalp
- face
- Anterior and posterior sweat ducts
According to current research, Malassezia yeasts are divided into twelve species.
The frequency of these yeasts on the skin of a healthy person depends primarily on the person's age. This is because increased sebaceous gland function only sets in during puberty. From this point onwards, colonization by Malassezia yeasts is attractive. Only with age and the associated lower sebum production does the colonization density decrease again.
Pityriasis versicolor (clover lichen) is the most common disease caused by a fungal pathogen of the Malassezia genus. The yeast responsible is Malassezia furfur.
In tropical regions, every second person is said to be affected. In temperate regions such as Germany, Austria and Switzerland, only 1 percent of the population is affected.
The Malassezia infection with pityriasis versicolor occurs in two different variants. Experts distinguish between:
- Pityriasis versicolor chromians and
- Pityriasis versicolor alba
Symptoms and appearance of pityriasis versicolor
Pityriasis versicolor chromians occurs in a hyperpigmented form. The hyperpigmentation usually appears in a roundish form. The spots occur particularly in sebum-rich areas of the skin. However, the condition can also occur on other areas of the body, such as the abdomen and arms.
The special characteristic is the variety of colors of the spots or hyperpigmentation. They are usually covered by scaling. Under a long-wave UV light, however, a yellow-green fluorescence appears.
Pityriasis versicolor is a skin disease in which the harmless skin fungus suddenly proliferates @ buraratn_100 /AdobeStock
If there is long-lasting depigmentation after the hyperpigmented spots have healed, experts speak of pityriasis versicolor alba.
This form of Malassezia infection mainly affects adults. It is difficult to treat. The infection only improves slowly. In any case, help from a specialist is needed.
It is not clear how such an infection occurs.
Doctors often believe that it is an allergic reaction caused by an increased density of Malassezia yeasts.
Other doctors, however, believe that these yeasts usually only have a pathological effect on certain risk groups. Risk groups include pregnant women and immunocompromised people.
Still other doctors suspect a connection between the risk groups and an allergic reaction.
It can therefore be said that hardly anyone is safe from a Malassezia infection. However, if you belong to one of the risk groups, you are more likely to fall ill.
Pityriasis versicolor is basically only a cosmetic problem. The hyperpigmented patches are long-lasting and spread over large areas of the skin.
Superficial mycosis is not dangerous and not life-threatening. However, you should not take the condition lightly and should have it examined by a specialist.
In some cases, superficial mycosis can degenerate into systemic mycosis. This happens when the skin is so severely affected that pathogens enter the body. In the case of systemic mycosis, the person's internal organs are attacked, which can lead to death.
The diagnosis is first made through a physical examination. The doctor takes a close look at the affected area and then takes a sample.
He usually scrapes off a few flakes of skin, which he then examines under a microscope. With the help of a so-called KOH preparation, the doctor can determine exactly whether a Malassezia infection is present.
If the doctor finds "spaghetti and meat balls" - accumulations of round sprout cells and hyphae - then a reliable diagnosis has been made.
Treatment usually takes the form of topical therapy. Doctors try to contain and destroy the pathogen with the help of an external application.
This usually involves the use of ointments, gels, special shampoos or creams. Patients apply the substances to the affected skin at regular intervals.
It is recommended to apply the ointments before going to bed in order to achieve a longer exposure time @ Ольга Тернавская /AdobeStock
This is important because there may also be pathogens around the source of the infection. You should make sure to thoroughly disinfect clothing that has come into contact with the mycosis. Only in this way can topical therapy be successful.
To ensure that topical therapy is effective, doctors also work with solutions that patients apply to the entire body.
This is mainly used if the spots are extensive.
So-called antimycotics are used in topical therapy. Antimycotics from the azole, ciclopiroxolamine and terbinafine groups are used. These have proven to be effective in studies.
This disease is also caused by Malassezia yeasts. However, this disease is not common. Affected people find it particularly annoying that the spots itch and pustules form.
Doctors also treat Malassezia infections with antimycotics, which usually lead to rapid relief of the symptoms.
- Malassezia dermatitis in animals
The disease can occur not only in humans, but also in animals. It is particularly common in dogs.
This disease is called Malassezia dermatitis. In dogs, it can often be diagnosed late, as most owners do not notice the symptoms. They think it is fleas. The thick coat also does not make it any easier for the owner to notice the disease visually.
Hyperpigmentation also occurs in an animal, usually affecting a large area. Skin thickening is also not uncommon. Dogs particularly often have to contend with infestation of the paws and claws.
Frequent licking of the paws is a typical alarm signal. Inflammation of the claw bed or discoloration of the claws can also be signs of mycosis.
If there is severe itching and redness, you should urgently consult a vet, as dogs often scratch themselves bloody. Scratching can allow pathogens to enter the body and cause more serious consequences. It also takes longer to heal and causes more pain for the animal.
The ears, underside of the neck, paws and armpits are often particularly affected @ weerachaiphoto /AdobeStock
Both humans and animals should seek medical advice and treatment for scaling and redness. You should seek treatment, especially for large patches. Even if Malassezia fungi are generally harmless, they can have serious consequences in some exceptional cases.