Seborrheic keratosis, also referred to as skin barnacles, are common non-cancerous skin growths with a characteristic “stuck-on” appearance. These are harmless and do not require treatment. However, they can occasionally become irritated or inflamed. If necessary, they can be removed by a doctor.
Table of Contents
What is seborrheic keratosis?
Seborrheic keratosis is a benign skin growth that occurs due to the proliferation of skin cells in the top layer of skin, known as the epidermis.
They tend to appear in middle-aged to older individuals, and the number of these “barnacle” skin spots can increase with age.
In fact, these are sometimes referred to as “senile warts,” but they are not true warts, which are skin growths caused by the human papillomavirus (HPV).
Other names used for seborrheic keratosis include seborrheic warts and wisdom warts.
Additional notes
Despite the name “seborrheic,” these growths have no relation to seborrhea or the distribution of oil glands. They are also not related to seborrheic dermatitis. (Read more: Seborrheic keratosis vs seborrheic dermatitis)
Pictures
Below, you can see images of seborrheic keratosis on different areas of the body.
Appearance and symptoms
Seborrheic keratoses are usually round or oval and can have a waxy or warty appearance. They may look as if they are stuck onto the skin’s surface, which is why they are called skin barnacles. They can range in size from a few millimeters to several centimeters.
These growths are generally elevated above the skin surface to form a papule or plaque, although sometimes seborrheic keratosis can be flat, especially in its early stages.
The color can vary — they may be skin-colored, yellowish, pink, gray, tan, brown, or black. While they usually have regular and well-demarcated edges, irritated or inflamed seborrheic keratosis can have irregular edges.
Seborrheic keratosis can appear on various parts of the body including the face, scalp, neck, legs, back, and chest. However, they are not found on the palms, soles, or mucous membranes, such as the lining of the mouth.
These growths can present either as individual spots or as clusters in specific areas, such as the groin, scalp, or under the breasts.
Note: If you’re curious about the term ‘barnacles,’ they are small crustaceans that attach to various surfaces in their natural environment. The term ‘skin barnacles’ is used to describe seborrheic keratoses because their appearance on human skin is similar to that of actual barnacles.
Are these itchy?
Seborrheic keratoses are usually asymptomatic but can become itchy, especially if they frequently rub against clothing or get caught in jewelry.
Types
There are different types of seborrheic keratosis mainly depending on their histology, meaning how they look under a microscope. Below are two types that are often mentioned:
Pigmented type
Pigmented seborrheic keratoses are those that show pigment and often appear as brown spots on the skin. This is generally due to an increase in melanin pigment in the skin cells.
This type can often resemble other pigmented skin lesions such as malignant melanoma, pigmented basal cell carcinoma, or melanocytic nevus (moles).
Irritated type
Irritated or inflamed seborrheic keratosis shows the presence of inflammatory cells in the skin. These can sometimes appear as pink spots or the area surrounding the seborrheic keratosis can be pink or red due to inflammation.
This type can often be confused with squamous cell carcinoma. However, they can be differentiated based on unique features under the microscope.
Variants
In addition to histologic types, there are a few variants of seborrheic keratosis. Some of these are:
- Stucco keratoses: These appear as small, white, gray, yellowish, or tan raised spots (papules) on the legs and ankles. These are commonly seen in elderly men.
- Dermatosis papulosa nigra: These appear as multiple small pigmented raised spots often on the face, especially around the eyes. These are typically seen in people with darker skin tones.
Causes
The exact cause of seborrheic keratosis is not known. However, they are often thought to be associated with sun exposure, aging, and genetic factors.
If your family members have these, you have a higher chance of having them as well. Seborrheic keratosis is not contagious and cannot spread through touch.
Are seborrheic keratosis related to cancer?
Seborrheic keratoses are not cancerous. However, an abrupt or sudden appearance of multiple growths, or a rapid increase in size or number of existing ones, may be associated with an underlying malignancy, commonly cancers of the gastrointestinal tract. This is called the sign of Leser-Trélat.
It’s worth mentioning that this concept is sometimes criticized. One reason for skepticism is that both the likelihood of developing seborrheic keratosis and the risk of cancer increase with age. This has led to questions about whether the two conditions are actually linked, or if the correlation is merely coincidental.
Additionally, the abrupt appearance of these growths can be triggered by other factors as well. For instance, certain medications or underlying inflammatory skin conditions can also cause a sudden increase in the number or size of seborrheic keratoses.
Therefore, if you experience any such changes, it’s important to consult a healthcare professional for proper diagnosis and treatment.
Look-alikes
Seborrheic keratosis can often be confused with other types of skin lesions which are discussed below. In some cases, a biopsy will be necessary to differentiate and make a diagnosis.
1. Melanocytic nevus (Mole)
Melanocytic nevi, commonly known as moles, are usually uniform in color, ranging from pink to dark brown. They are symmetrical and have defined borders.
Moles are generally smooth to the touch and may sometimes be raised but lack the ‘warty’ or ‘scaly’ texture that is characteristic of seborrheic keratosis.
2. Warts
Warts are flesh-colored to light brown and round or oval in shape. Unlike seborrheic keratosis, warts do not have a pasted-on appearance. Warts can also spontaneously resolve over time and are more likely to occur in areas of skin trauma.
3. Actinic keratosis
Actinic keratosis can range in color from pink to brown and often has irregular borders that are not as well-defined as those in seborrheic keratosis. However, keep in mind that inflamed seborrheic keratosis can have irregular edges.
Also, actinic keratosis is a precancerous lesion and may progress to squamous cell carcinoma in some cases.
4. Melanoma
Melanoma is often multicolored with shades of brown, black, or even blue. It usually has an irregular shape and blurred or jagged borders. Melanoma can be a flat or raised skin lesion. Unlike seborrheic keratosis, melanoma shows rapid growth and often is a single spot.
5. Basal cell carcinoma
Basal cell carcinoma is often translucent, pearly, pink, and skin-colored and frequently appears raised with visible blood vessels. Some can have melanin pigment and are called pigmented basal cell carcinoma.
Unlike seborrheic keratosis, it may have a central depression or rolled edges. It also often has a smoother, more ‘pearly’ appearance, as opposed to the rough, ‘warty’ texture of seborrheic keratosis. Basal cell carcinoma may ulcerate or bleed, which is less common in seborrheic keratosis.
6. Squamous cell carcinoma
Squamous cell carcinoma often appears as a firm, red nodule or as a flat lesion that may have a crusted or scaly surface, which can sometimes make it look similar to seborrheic keratosis. However, unlike seborrheic keratosis, these lesions tend to grow more quickly.
Diagnosis
Diagnosis is generally based on the characteristic clinical appearance of skin barnacles. Dermoscopy, which involves examining lesions with a handheld device, may be helpful.
If required, a biopsy or full excision may be performed for further examination under a microscope by a pathologist.
Can these be removed at home?
There are no proven over-the-counter creams or lotions specifically designed to effectively remove seborrheic keratosis. It’s not advisable to attempt treating them at home using strong acids or other DIY treatments.
Doing so could lead to complications such as infection or scarring. Instead, consult a healthcare professional for proper management.
Treatment
Although treatment is usually not necessary, seborrheic keratosis can be removed for symptomatic relief or cosmetic reasons by a doctor. Below are some common procedures and topical treatments for removal.
1. Cryotherapy
Cryotherapy involves freezing the growth with liquid nitrogen. The rapid freezing destroys the cells, causing the lesion to eventually fall off or peel away.
Smaller or flat lesions may require 1-2 sessions, while thicker lesions may require multiple sessions. This treatment may lead to skin discoloration, especially in those with darker skin tones.
2. Curettage
Curettage involves using a curette, a cup-shaped instrument, to scrape off the lesion along with a thin layer of skin. Local anesthesia is used to numb the area before the procedure. The tissue can be sent to a pathology lab to confirm the diagnosis.
3. Electrocautery
Electrocautery involves burning the skin growth with an electric current. The area is numbed before the procedure. This method is often used in conjunction with curettage.
4. Lasers
Lasers offer a non-surgical option, although results may vary. Two types of lasers are commonly used: ablative lasers, which injure the top layer of skin, and non-ablative lasers, which are less invasive and do not affect the top layer of skin.
5. Shave excision
Shave excision involves using a scalpel to shave off the growth, which can then be sent to a pathology lab for examination.
6. Topicals
There are a few topical treatments for seborrheic keratosis that may help in reducing the size or even removing them completely, although results can vary. These include:
- Vitamin D3 ointments
- Nitro-zinc solution
- Tazarotene 0.1% cream
- 5% potassium dobesilate cream
- High-strength trichloroacetic acid (TCA) peel
- 1% diclofenac sodium solution
- Urea-based topicals
Hydrogen peroxide at a 40% concentration was approved by the FDA for treating seborrheic keratosis, however, recently it was discontinued.
It’s important to consult a healthcare professional for proper diagnosis and to determine the most appropriate treatment for your condition.
When to see a doctor
One should consult a doctor if:
- There is a sudden increase in the number or size of seborrheic keratosis.
- New symptoms appear, such as itching, bleeding, or ulcer formation.
- The barnacle spots have irregular edges.
- The growths frequently get caught in clothing or jewelry.
- You are unsure of the cause of the lesion.
Key points
“Skin barnacles” is a common term often used for seborrheic keratosis due to its characteristic appearance. These spots can vary in color and are often raised with a warty or rough texture.
They can be easily confused with other skin conditions, especially pigmented and inflamed types that resemble skin cancers like melanoma or squamous cell carcinoma.
If you notice any new changes or are uncertain about a skin lesion, it’s best to consult a dermatologist for a thorough examination.
References
- Metin SA, Lee BW, Lambert WC, Parish LC. Dermatosis papulosa nigra: a clinically and histopathologically distinct entity. Clin Dermatol. 2017 Sep-Oct;35(5):491-496. Epub 2017 Jun 8. PMID: 28916031.
- Carrera C, Segura S, Aguilera P, Scalvenzi M, Longo C, Barreiro A, Broganelli P, Cavicchini S, Llambrich A, Zaballos P, Thomas L, Malvehy J, Puig S, Zalaudek I. Dermoscopic Clues for Diagnosing Melanomas That Resemble Seborrheic Keratosis. JAMA Dermatol. 2017 Jun 1;153(6):544-551. PMID: 28355453; PMCID: PMC5540029.
- Mansur AT, Yildiz S. A diagnostic challenge: inflamed and pigmented seborrheic keratosis. Clinical, dermoscopic, and histopathological correlation. Dermatol Online J. 2019 Mar 15;25(3):13030/qt0w56m5hq. PMID: 30982311.
- Mitsuhashi Y, Kawaguchi M, Hozumi Y, Kondo S. Topical vitamin D3 is effective in treating senile warts possibly by inducing apoptosis. J Dermatol. 2005 Jun;32(6):420-3. PMID: 16043912.
- Eksomtramage T, Aiempanakit K. Verruca plana mimicking seborrheic keratosis in the elderly: A case report. IDCases. 2019 Nov 1;18:e00661. PMID: 31754601; PMCID: PMC6854063.
- Mirali S, Mufti A, Lansang RP, Sachdeva M, Yeung J. Eruptive Seborrheic Keratoses Are Associated With a Co-Occurring Malignancy in the Majority of Reported Cases: A Systematic Review. J Cutan Med Surg. 2022 Jan-Feb;26(1):57-62. Epub 2021 Nov 28. PMID: 34841905; PMCID: PMC8750131.
- Hydrogen Peroxide 40% (Eskata) for Seborrheic Keratoses. JAMA. 2019;321(1):99–100. doi:10.1001/jama.2018.16100
- Nicole Natarelli, Amanda Krenitsky, Kerry Hennessy, Sarah Moore & James Grichnik (2023) Efficacy and safety of topical treatments for seborrheic keratoses: a systematic review, Journal of Dermatological Treatment, 34:1.
Disclaimer: This article is for information purposes only and does not replace medical advice.