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Tinea nigra is a skin fungal infection where there are dark brown to black spots, mainly on the hands (palms) and feet (soles). It can be caused by uncommon skin fungi known as dermatophytes, and these fungi only consume the outermost layers of the skin.
Unlike other common skin fungi, tinea nigra is not typically itchy. The word tinea refers to dermatomycosis, a superficial dermatophyte skin infection. Other tine infections, like those on the scalp (tinea capitis), feet (tinea pedis), and groin (tinea cruris), tend to present with the typical ring-like lesion and are often referred to as ringworms.
What does tinea nigra look like?
Tinea nigra is a superficial fungal infection that can often resemble a brown or black patch on the skin. This condition is caused by a fungus known as Hortaea werneckii, also referred to as Cladosporium werneckii or Exophiala werneckii. Tinea nigra is commonly found on the palms or soles of the feet, making it a noticeable skin issue. Although this condition is more prevalent in tropical or subtropical regions, cases have been reported in the United States as well.
It’s important to note that while tinea nigra is typically harmless, it’s crucial to distinguish it from other skin conditions, including skin cancer. Being vigilant about any unusual skin patches and seeking medical advice can ensure proper diagnosis and treatment, particularly in regions like Central and South America where tinea nigra is more commonly encountered.
Symptoms of Tinea Nigra
The typical tinea nigra rash is round to oval in shape, although it can also have an irregular shape that is somewhat circular. The color of the rash varies from light to dark brown, and even black in some individuals. The reason for this difference lies in a person’s natural skin color (pigmentation). The typical darkening in tinea nigra is due to the concentration of melanin at the site where the fungus invades the skin. Despite it occurring mainly on the palms of the hands, and soles of the feet, the tinea nigra spots can also be seen elsewhere at times – like on the chest and neck.
Tinea nigra is not itchy and this can sometimes be confusing as most fungal infections of the skin tend to itch. It grows slowly over weeks and months and may not cause the typical destruction of the skin marked by drying and cracking. There is a clearly demarcated border between the darkened skin and the health normal-colored skin. The red raised border seen with other tinea infections (ringworm) is absent. Most of the time tinea nigra present with a single dark brown to black spot that varies in size from a few millimeters to several centimeters. Multiple spots is possible although uncommon.
Why does tinea nigra occur?
Causes and Risk Factors
Tinea nigra is a skin infection caused by fungi. There are various species of fungi that cause this type of infection and most of these fungi are uncommon. These fungi include Cladophialophora saturnica, Cladosporium werneckii, Exophiala werneckii, Hortaea werneckii, Phaeoannellomyces werneckii or Stenella araguata. The most common cause is Phaeoannellomyces werneckii.
As the skin invade and destroy the outer skin, it consumes the natural pigment in human skin – melanin. The pigment then becomes concentrated within the fungi giving it the brown to black appearance. People with more melanin (darker-skinned people) will therefore experience darker brown, almost black, rashes.
People who work with soil are at a higher risk of developing tinea nigra. The brown mold, Phaeoannellomyces werneckii, is found in soil and compost and tends to infect people with sweaty palms and feet (hyperhidrosis). Gardeners and farm workers are therefore more likely to develop tinea nigra and should use gloves and boots that limits their contact with the soil. Since the tine nigra fungi transfer from the soil to humans, it is known as geophilic fungi.
How is tinea nigra diagnosed?
Skin Tests for Tinea Nigra
The diagnostic methods for confirming tinea nigra is not significantly different from other fungal infections of the skin. Scrapings of the affected skin can be examined under the microscope using a potassium hydroxide mouth. This can be further confirmed by growing the fungi sourced from the skin scrapings in the laboratory – fungal culture. Although the typical appearance of tinea nigra coupled with a positive history of soil contact may be sufficient for a diagnosis, these laboratory tests should be undertaken. Some cancerous skin lesions like melanoma may present in a similar way, although the palms and soles are uncommon sites for these cancers.
How is tinea nigra treated?
The treatment of tinea nigra typically involves the use of topical antifungal agents, such as salicylic acid. In some cases, a skin biopsy may be necessary to confirm the diagnosis, especially if the brown or black patch is on the palms or soles of the feet. Dermatologists may prescribe appropriate medications to manage this superficial fungal infection effectively.
Treatment for Tinea Nigra
The treatment for tinea nigra is not significantly different from other dermatophyte infections. Topical treatment is all that is necessary in most cases. These skin applications contain antifungal ingredients such as clotrimazole, ketoconazole, miconazole and terbinafine. It should be used for a period of 2 to 4 weeks although more persistent fungal infections may require treatment for up to 6 to 8 week.s
Oral treatment (antifungal pills) are not usually necessary for tinea nigra. However, to expedite the treatment of the infection, the affected area may first be scraped with a scalpel to allow the antifungal cream or ointment to penetrate deeper. Apart from medical treatment, patients need to be made aware of the importance of reducing contact with the source of the fungi, like soil and compost. Gardening gloves and work boots are usually sufficient measures.
She is a skilled dermatologist, guides individuals to achieve radiant and healthy skin. Her expert-backed insights and gentle care help individuals feel confident and beautiful in their own skin.
