Many people have been afflicted with warts in different parts of their bodies, and correctly identifying them isn’t very difficult.
Sometimes, though, warts don’t look like what people would normally expect, or they start out looking normal but change their appearance after a while. This includes warts turning black or warts that have black dots in them.
What happens when a wart turns black?
There are various reasons why warts turn black. Often, the skin surrounding warts start to thicken, giving wart a look like a callus. But it has been observed in various cases that warts turn black just before they start to disappear on their own. [26]
Two main types of warts exist: cutaneous and genital.
The former is further divided into groups depending on their location and appearance, which usually corresponds to one of the many different subtypes of the virus causing warts: the human papillomavirus (HPV).
There are many reasons that can cause warts to appear black or to change their color to black after some time. Blackening can be seen in all types of warts, cutaneous and genital, including the subtypes.
Cutaneous Warts
Also known as common warts, they are one of two main types of warts, they can appear anywhere on the body including the genitals. [1]
They are caused by HPV subtypes 1, 2, 4, 27, and 57,[2] and have several different forms and locations that they commonly afflict. [3]
- Common warts: small, firm bumps with a rough surface, that can grow to about 1 cm. Multiple warts can be found, and they can fuse to form a large mass.
- Periungual warts: common warts that are found around the nails, and are predisposed to by nail-biting and thumb sucking.
- Plantar warts: common warts that grow on the soles of the foot and undersurface of toes, they can be multiple and may fuse together forming what is called mosaic plantar warts.
- Plane warts: also known as flat warts, these are round, smooth, skin-colored bumps, that can be found in hundreds over the body. They can sometimes fuse together forming lines that have been infected by the virus by scratching.
- Filiform and digitate warts: more common in males, these warts have filaments or fingers projecting out from them. They mostly afflict the scalp, face, and neck.
Several reasons may result in cutaneous warts turning black depending on their location and conditions.
Common Warts on the Fingers and Elsewhere
One of the more common (and, indeed, most reassuring) reasons for warts turning black is that they are healing. Common warts, when regressing, have been known to turn black, but that occurs infrequently.
What is more common is that healing of the wart can be preceded by inflammation, itchiness, redness, and swelling. This may cause the person afflicted to become aware of warts to which they were previously oblivious.[4]
Seed Warts
Sometimes a cutaneous wart will appear black from the start. This type of wart is often called a “seed” wart because it appears to have a black core resembling a seed. This is actually a misnomer, as this seed is nothing more than blood vessels infiltrating the substance of the wart.[5] This phenomenon is more common in certain types of warts, such as plantar warts. [6]
Sunlight can aggravate seed warts by increasing their rate of growth and possibly resulting in an increase in blood supply to the wart and more blackening. Seed warts can be so proliferative that one person can have dozens of even hundreds of them. [7]
Plantar and Mosaic Warts on the Feet and Toes
The plantar wart is considered a subtype of the common wart that affects the sole of the foot, which is known as the plantar aspect. They have a characteristic, well-defined appearance, with a rough surface and a smooth line of demarcation between them and normal skin.
Plantar warts can usually be found on points on the foot that are exposed to pressure. These are areas that have bony prominences underneath the skin and carry the weight of the body. Examples include the heel and the ball of the foot or the toes. This may make them painful to apply pressure during walking and standing.
Sometimes, plantar warts are multiple and close together, and may even fuse together to form a large contingent mass of warts resembling a mosaic and is known as mosaic plantar warts. [8]
Plantar warts, when healing, are known to become inflamed, and blackening is more common than in common warts. This blackening is due to clotting in blood vessels that grow inside the wart.[9]
Seeding is more common in plantar warts, as stated above.
Pigmented Warts
Among cutaneous warts that start out black is the pigmented wart. These warts have been found in certain ethnicities, such as Japanese, and have been documented on their soles and palms.
Microscopic examination of these warts has shown that the cells have increased number of melanosomes, which are intracellular granules that are responsible for production, storage, and transport of melanin[10], the pigment that gives skin, hair, and eyes their color.[11] The presence of melanosomes in warts is associated with HPV types 4, 60, and 65. [12]
Genital Warts
Also called ano-genital warts, these are the other main type of warts, which can also turn black.
- These are caused by HPV subtypes 6 and 11, and very rarely by subtypes 1 and 2.[13]
- They are transmitted sexually to the genitals, and may be transmitted to the anus either sexually or through local spread from the genitals. [14]
- They usually take the form of soft, pink swellings with a cauliflower-like surface, called condyloma acuminata or the acuminate form. [15]
- Genital warts usually don’t have any symptoms, but they can sometimes cause a bad odor, discharge from the genitals or bleeding. [16]
Other than the acuminate form, other forms of genital warts are flat, but are more obvious than plane warts. When they are found in the skin of the genitals (and not the mucous membranes), they may be pigmented. This pigmentation may result in the wart having a dark brown, almost black color. [17] To know more about how genital warts evolve check out our article about early signs & symptoms of genital warts.
Black warts caused by treatment
In addition to warts being black from the start, or turning black due to disease progression or regression, sometimes warts can turn dark or black because of the methods used to treat them. An ingredient used in wart treatment cream called 5-fluorouracil can cause redness or hyperpigmentation of warts, which makes them dark brown or almost black. [18]
Another treatment option is the injection of an antibiotic called bleomycin (which is used to treat some cancers)[xix] into the wart itself[20], a method known an intralesional bleomycin injection. This has been reported to cause some pigmentation at the site of injection. [21]
Other causes of black “warts”
Some special forms of HPV infection may result in the formation of pigmented warts. Other skin conditions that closely resemble warts may also be culpable in the appearance of black wart-like lesions. Some warts may also undergo malignant transformation, giving rise to different types of cancer, which may undergo blackening due to blood clotting or death of tissues.
Epidermodyplasia verruciformis
This is an inherited disease where a person has a longstanding and widespread HPV infection. It presents with multiple plane warts among other features, and can very commonly progress to cancer in adults. Warts on the face and neck are very similar in appearance to plane warts, but further down on the trunk and on the limbs they are larger, and can either be depigmented and lighter than normal skin, or hyperpigmented and brown. Thick plaques may form which can be violet or brown in color.
Seborrheic Keratosis
Another common skin condition that causes brown or black wart-like swellings, seborrheic keratosis is the most common non-cancerous skin growth in older adults, and are sometimes called seborrheic warts.
The role of HPV in seborrheic keratosis has been suggested, but no substantial evidence has been established. The growths are light tan, brown, or black, and appear on the face, chest, shoulders, or back. [22]
Seborrheic keratosis is a benign condition that doesn’t progress to cancer. It is painless and requires no treatment unless it is cosmetically distressing. [23]
So, what people think are black warts, may actually be seborrheic keratoses.
Cancers and Ano-Genital Intraepithelial neoplasia
Cutaneous warts’ progression to cancer is extremely rare but may be more common in persons with compromised immunity.
Genital warts could progress to cancers a bit more commonly, due to the possibility of infection with high-risk subtypes of HPV that are associated with malignant transformation.
Several types of cancer can be associated with HPV infection, such as:[24]
- Squamous cell carcinoma including head and neck squamous cell carcinoma
- Cervical carcinoma
- Ano-genital intraepithelial neoplasia, which includes the following types:
- Cervical intraepithelial neoplasia
- Vulval intraepithelial neoplasia
- Anal intraepithelial neoplasia
- Penile intraepithelial neoplasia
- Other ano-genital cancers
- Laryngeal carcinoma
Tissue necrosis in cancers may cause blackening of the lesions. The appearance of any ano-genital warts should raise the possibility of infection with a high-risk HPV subtype, and warrants screening for ano-genital intraepithelial neoplasia. [25]
[thrive_text_block color=”light”] Bottom Line: There are myriad reasons that could result in warts turning black, or the appearance of brown, or dark pigmented skin growths. Regression of the warts is probably the most common cause, but other causes can include some treatment options, the appearance of blood vessels in the wart, blood clotting, pigment deposition, and malignant transformation.[/thrive_text_block]
References:
[i] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.47-25.50.
[ii] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.46.
[iii] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.47-25.50.
[iv] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.50.
[v] https://www.webmd.com/skin-problems-and-treatments/plantar-warts-palmer-warts#1
[vi] http://moleremovalat.com/types-of-warts/seed.html
[vii] http://www.healthcentre.org.uk/cosmetic-treatments/wart-seed-warts-treatment.html
[viii] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.47-25.50.
[ix] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.50.
[x] http://jcs.biologists.org/content/121/24/3995
[xi] https://www.medicinenet.com/script/main/art.asp?articlekey=4340
[xii] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.50.
[xiii] Aubin F, Pretet JL, Jacquard AC, et al. Human papillomavirus genotype distribution in external condylomata: a large French national study (EDiTH IV). Clin Infect Dis 2008;47:610–15. 229
Arima Y, Winer RL, Feng Q, et al. Development of genital warts after incident detection of human papillomavirus infection in young men. J Infect Dis 2010;202:1181–4. 230
Krzyzek RA, Watts SL, Anderson DL, et al. Anogenital warts contain several distinct species of human papillomavirus. J Virol 1980;36:236–44.
[xiv] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.55.
[xv] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.55.
[xvi] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.56, 25.57.
[xvii] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.57.
[xviii] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.52.
[xix] https://radiopaedia.org/articles/bleomycin-lung-toxicity
[xx] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.54.
[xxi] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.54.
[xxii] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 133.1-133.2.
[xxiii] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 133.1-133.2.
[xxiv] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.44-25.45
[xxv] Griffiths CEM, Barker J, Bleiker T, Chalmers R, Creamer D. Rook’s Textbook of Dermatology. Vol 2. 9th ed. West Sussex, UK: Wiley-Blackwell; 2016; 25.57
[xxvi] Plantar warts recently turned black. Clinical and histopathologic findings. https://www.ncbi.nlm.nih.gov/pubmed/7059201 1982 Jan;118(1):47-51. Authors – Berman A, Domnitz JM, Winkelmann RK.