Seborrheic keratosis is one of the most common non-cancerous (benign) skin growths, and is thought of as a normal part of skin aging, most found in adults greater than 40 years of age. Seborrheic keratosis are completely harmless, typically presenting as waxy, raised, wart-like lesions with a variation in color from light tan to black. Generally, they are not contagious, and are not caused by cancer, although they may sometimes look like skin cancer (melanoma) or be of concern due to their resemblance to skin cancer.

Seborrheic keratosis are commonly referred to as the “barnacles of aging,” because they develop typically later in life, and many can develop at time. Seborrheic keratosis can develop on any surface of the body, most often on the trunk or back, except for the palms and soles. Seborrheic keratosis are most commonly found on the chest, back, scalp, face or neck.

Seborrheic keratosis arise due to excessive proliferation of keratinocytes, the predominant cell type in the outer layer of the skin (epidermis). The exact cause of seborrheic keratosis is still not known, although they are not the result of viral infection or poor hygiene and are not premalignant (precancerous).

Treatment is usually not necessary unless the lesions bothersome, inflamed or a cosmetic concern. Seborrheic keratosis can be safely removed for comfort or cosmetic reasons, if desired.

While the underlying cause of seborrheic keratosis is not fully understood, it should be noted that these growths are not viral, bacterial or contagious in nature. Furthermore, there are no known preventative measures for seborrheic keratosis. Several contributing factors appear to be associated with the development of seborrheic keratosis:

• Age: Age is the biggest risk factor. Seborrheic keratosis are rarely seen in children but are most often seen in individuals older than forty. They affect men and women equally, and as we age, the number and size of these lesions tends to increase.
• Genetics: There seems to be a genetic component. Individuals with a family history of seborrheic keratosis are more likely to develop seborrheic keratosis, suggesting genetic predisposition.
• Sun exposure: Seborrheic keratosis tend to be seen more often in areas of the skin that have had a chronic amount of sun exposure (e.g., face, arms, back), suggesting that ultraviolet (UV) radiation might indirectly contribute to their development.
• Skin irritation or friction: These growths usually appear in areas of skin that experience a lot of friction or rubbing (e.g., armpits, groin area, and beneath the breasts). Chronic skin irritation may contribute to their presence in those regions.
• Hormonal Changes: Fluctuation of hormone levels may lead to the sudden emergence of seborrheic keratosis. For instance, pregnant women or women receiving estrogen replacement therapy may experience new lesions as a result of hormonal changes.
• Paraneoplastic Sign (Leser-Trélat Sign): In rare situations, the instantaneous appearance of multiple seborrheic keratosis may be indicative of an underlying internal malignancy—particularly in the case of gastrointestinal cancers—in which case you would want to seek medical evaluation for further inquiry. This is referred to as the Leser-Trélat sign. 
• Skin Tone: Individuals with lighter pigments more commonly describe seborrheic keratosis, although they can occur in people of any skin color.

Seborrheic keratosis can appear instantaneously or grow gradually over time, and range dramatically in size, shape and color. Most lesions are asymptomatic, but some lesions may be irritated or itchy (especially when garments, jewelry, or shaving rub the area).

Common Characteristics Include:

• Color: Generally tan, brown, or black either way some lesions may be lighter and darken with time.
• Texture: Usually waxy, scaly or rough in texture. They may look like they were a “pasted on” piece of skin similar to a blob of wax or clay.
• Shape and Size: These lesions may vary from only a few mm to over 2.5 cm (one inch) in diameter.
• Surface Appearance: The lesions may be flat or raised, often appearing wart-like with a crusty or bumpy surface.
• Location: The most common locations for the lesions are on the face, chest, back, shoulders, and scalp. The lesions do not form on the palms of the hands or the soles of the feet. Number: People with seborrheic keratosis can have anywhere from one to dozens or even hundreds as they age.
• Symptoms: In most cases, they are painless but can become itchy, red, or even bleed even if slightly scratched or irritated, or snagged on clothing.

Though seborrheic keratosis are benign skin lesions, you should see a healthcare provider if your skin lesion:

• Changes in size, color or shape
• Bleeds, itches excessively or is painful
• Does not heal
• Has irregular or poorly defined borders

In these instances, your doctor may want to perform a biopsy to rule out skin cancer, especially melanoma or basal cell carcinoma.

When these lesions appear in clusters in individuals with darker skin tones, and especially if they are present on the face or around the eyes, they are called dermatosis papulosa nigra (DPN). This variant tends to be common in people with Black or brown skin; it is often considered a cosmetic issue as opposed to a medical issue.

Seborrheic keratosis is most often diagnosed on clinical grounds, meaning that a provider, normally a dermatologist, will simply be able to identify it with visual inspection alone. If the lesion is atypical or has features resembling skin cancer, one may take more steps from a clinical perspective to exclude conditions of greater concern.

Diagnostic Methods:

1. Physical Examination: A dermatologist will evaluate the lesion’s appearance, texture, location and patient history. Most seborrheic keratosis have that classic “pasted-on” look, which is usually recognizable in a routine skin examination.
2. Dermatoscopy (or Dermoscopy): This is a handheld digital dermatoscope used to magnify and illuminate the skin, enabling the physician to examine surface patterns and surface pigmentation more closely. This is particularly helpful when differentiating seborrheic keratosis from melanoma or basal cell carcinoma.
3. Skin Biopsy: If the lesion appears atypical, for example, growing quickly, changing in appearance, encroaching other moles, bleeding or suspect in nature, the dermatologist will often recommend a biopsy. A skin biopsy often involves removal of the entire lesion or a small sample to be examined microscopically to help confirm a diagnosis and rule out malignancy. 
4. Differential Diagnosis: Seborrheic keratosis can mimic many other skin conditions, so a thorough assessment is warranted. Some of these conditions include:
   • Melanoma (skin cancer) 
   • Basal cell carcinoma (skin cancer) 
   • Warts (verruca vulgaris) 
   • Actinic keratosis 
   • Moles (nevi) 

     Proper diagnosis is important to identify seborrheic keratosis from cancerous or precancerous skin lesions as well as to help determine whether further treatment or assessment is needed.

Seborrheic keratosis are benign, and generally, treatment is not needed unless they become irritated, cosmetically bothersome, or there is concern over the diagnosis. Although they do not resolve on their own, they can be removed by a number of safe and efficacious methods when treatment is desired.

Common Treatment Methods:

1. Cryosurgery: This is the most common method. A tumor is frozen with liquid nitrogen, allowing it to fall off all together after time has passed. There is a minimum of invasiveness involved, but it can result in redness, blistering or light patches of skin temporarily. It becomes less effective for thicker or very raised growths. 
2. Curettage: The lesion is scraped off with a wide surgical tool, called a curette. This is done under local anesthesia, and if required, can be done with electrosurgery for better efficacy. 
3. Electrosurgery: An electric current is applied and burns off the lesion. The lesions in most cases are numbed first. This modality would often be employed in lesions which are thicker or tougher, with the scrape off sometimes required afterwards or it would fall off in time.
4. Laser Therapy: A concentrated beam of light is used to destroy the lesion, with minimal damage to surrounding skin. Many people go for laser because they want to make a cosmetic decision, and in particular on the face, and the cosmetic results are very good.
5. Shave Excision: The site’s lesion is shaved using a scalpel and local anesthesia. This method is preferred when one is also doing a biopsy to confirm diagnosis.
6. Topical Treatments (Research/Selective use):
   • Hydrogen Peroxide 40% Solution (Eskata):  FDA approved for use in raised seborrheic keratosis treatment. The use of this is limited and may not successfully treat all patients.
   • Nitric Acid–Zinc Solution (Nitrizinc Complex):  This is a mixture of nitric acid, zinc, copper salts and organic acids. In one small study in 2019, it was noted to be safe and effective in decreasing or eliminating most lesions within 6 months.

Post-Treatment Care

• Keep the area clean and dry.

• Apply antibiotic ointment per instruction.

• Do not scratch or pick the area not to solicit an infection or scarring.

Seborrheic keratosis is a benign yet common skin lesion that typically develops with age. While the exact causes are unknown, elements such as age, genetics and possibly the build-up of sun exposure all play into the ideas about the disease. Seborrheic keratosis are involuntary and benign in nature, and typically not itchy; however, they sometimes present like important diseases such as malignant melanoma. Therefore, it is imperative to have any unusual or changing skin lesions assessed by a healthcare professional. 

The good news is that seborrheic keratosis does not require treatment unless the lesion is bothersome through itch or unappealing. When treatment is wished, there are many camouflaged treatments or effective methods of treatment that are considered safe and include cryotherapy, electrosurgery, curettage, laser therapies, and selective topical therapies. 

Patients should self-assess their skin lesions for changes and should also notice if new skin lesions are suspicious in nature. Regular examinations with a dermatologist are also constructive if the patient has many moles or skin lesions and it may also offer reassurance and to encourage possible early diagnosis of serious skin conditions. In knowing about seborrheic keratosis and understanding that it is a benign condition, patients can have more comfort in permitting a further medical evaluation only when necessary. By maintaining a good skincare program, awareness of the skin, and routine evaluations, most people with seborrheic keratosis can adequately manage the condition with good cosmetic outcomes.

• MedlinePlus. (2022). Seborrheic keratosis. U.S. National Library of Medicine.
• Habif, T. P. (2022). Seborrheic keratosis. Medscape
• American Academy of Dermatology Association. (n.d.). Seborrheic keratosis: Diagnosis and treatment. Retrieved June 13, 2025