Seborrheic keratosis: information for patients

Seborrheic keratosis is one of the most common benign skin lesions in adults. It typically appears as a raised, rough, waxy, or «sticky» patch or bump on the skin. While not considered a precancerous lesion in itself, it can resemble other lesions that do require investigation, such as actinic keratosis, basal cell carcinoma, squamous cell carcinoma, or melanoma. Therefore, the key is not to panic, but to know when to observe it and when to consult a doctor.

Summary in 60 seconds

• Seborrheic keratosis is a benign growth of the superficial layer of the skin.
• It appears more frequently from middle age onwards and increases with age.
• It can be brown, black, beige, pink, or whitish.
• Its typical appearance is that of a «stuck», waxy, warty or rough lesion.
• It is not contagious and is not caused by a lack of hygiene.
• It doesn’t usually hurt, although it may itch, become irritated, or bleed if rubbed or scratched.
• It is not recommended to pull it out, burn it, or treat it with home remedies.
• It is advisable to check if it grows quickly, changes color, bleeds, hurts, or looks different from the others.
• The dermatologist usually evaluates it with clinical examination and dermatoscopy.
• If there is any doubt, a biopsy or excision may be indicated for microscopic study.

What are seborrheic keratoses?

Seborrheic keratosis is a benign growth of the epidermis, the outermost layer of skin. It originates from the proliferation of superficial skin cells, especially keratinocytes. In medical literature, it may also appear as «seborrheic wart» or «basal cell papilloma,» although these names can be confusing and are therefore no longer commonly used.

Despite being called «seborrheic,» it does not originate from skin oil or sebaceous glands. It is also not a viral wart. It is not contagious through contact, cannot be transmitted to other people, and is not caused by poor hygiene. Current evidence describes it as a very common benign lesion, primarily related to age, individual predisposition, and possibly sun exposure in some people. (Barthelmann 2023 , Sun 2022)

There may be only one lesion, but many people develop several over time. In darker skin tones, there is a common variant called dermatosis papulosa nigra , which appears as small, dark papules, especially on the face, neck, and around the eyes.

Why does it appear?

The exact cause is not fully understood. It is more prudent to speak of contributing factors, not a single cause.

The most consistent factor is age. Seborrheic keratoses usually appear in adulthood and become more frequent with age. There may also be a familial predisposition: some people develop many lesions because they have an inherited tendency.

Sun exposure may contribute in some cases, especially when they appear on the face, neck, chest, shoulders, or backs of the hands. However, they can also appear on covered areas, such as the torso, back, or abdomen; therefore, it is not considered a complete explanation. Friction, skin irritation, and certain medical treatments may play a role in specific cases, but they do not explain most cases.

It is important to differentiate it from other conditions:

• Actinic keratosis: a rough lesion related to sun damage, considered precancerous.
• Moles or nevi: melanocytic lesions that may appear pigmented.
• Melanoma: skin cancer that can mimic benign lesions.
• Basal cell or squamous cell carcinoma: some tumors may have crusts, pigment, or raised relief.
• Viral warts: caused by the human papillomavirus; seborrheic keratosis is not.

What does it look like and what symptoms does it cause?

Their appearance can vary greatly. Some are small, flat, and inconspicuous; others are thick, warty, or pigmented. The classic description is that of a lesion that appears to be «stuck» to the skin, like a drop of wax or an adherent scab.

It can be presented as:

• Brown, black, beige, grayish, pinkish or whitish spot or plaque.
• Rough, waxy, scaly or warty surface.
• Well-defined edges.
• Variable size, from a few millimeters to several centimeters.
• Location on trunk, back, chest, abdomen, face, neck or scalp.
• Usual absence in palms, soles and mucous membranes.

It generally doesn’t cause symptoms. Some people notice itching, tenderness, or irritation when the lesion rubs against clothing, jewelry, shaving, or other friction. If scratched or traumatized, it may become inflamed, crust over, or bleed.

Here’s the important clinical point: a seborrheic keratosis can be benign, but a lesion that «looks» like a seborrheic keratosis isn’t always so. Dermatoscopic studies have shown that some malignant lesions, including melanoma, can clinically mimic it; therefore, any new, changing, or distinct lesion warrants evaluation. Carrera 2017 , Diep 2021

What can you do today?

The safest thing to do is to observe carefully, take care of your skin, and consult a doctor when there are signs of change.

You can start by examining the lesion in good light, without touching it. Take a clear, dated photograph if you want to track its progress. There’s no need to obsess over checking it daily; for stable lesions, monthly observation is usually more than reasonable.

If the lesion is irritated by rubbing, avoid unnecessary friction. Wearing looser clothing, protecting it from direct shaving, or temporarily covering it if it gets caught on clothing or accessories can help. If the surrounding skin is dry or sensitive, a simple moisturizer can reduce dryness and discomfort, although it won’t eliminate the lesion.

Sun protection is a generally healthy measure: it doesn’t «cure» seborrheic keratosis, but it reduces cumulative sun damage and helps prevent other skin lesions related to ultraviolet radiation. Use broad-spectrum sunscreen, shade, a hat, and protective clothing depending on your sun exposure.

Consult a dermatologist if the lesion concerns you, if it becomes frequently irritated, or if you wish to have it removed for convenience or cosmetic reasons. Medical treatments include cryotherapy with liquid nitrogen, curettage, electrosurgery, laser treatment, or superficial excision, depending on the case, location, skin type, and suspected diagnosis. The choice of method should take into account realistic expectations: the lesion may result in a lighter or darker area, a small scar, or local recurrence.

What NOT to do?

Do not try to pick, cut, burn, or «dissolve» it at home. Even if it seems superficial, manipulating it can cause bleeding, infection, scarring, or pigmentation changes. Furthermore, removing a lesion without a diagnosis can delay the identification of a malignant lesion that resembled seborrheic keratosis.

It is also not advisable to apply acids, caustics, wart products, home remedies, or viral treatments without medical advice. Seborrheic keratosis is not a viral wart; therefore, many products designed for warts are unsuitable and can irritate the skin.

Avoid assuming that every raised brown lesion is benign. The dermatologist’s expertise, dermatoscopy, and, when appropriate, biopsy exist precisely because some lesions share visual characteristics.

When should I consult?

Consult a dermatologist if any of these signs appear:

• Rapid growth.
• Recent change in color, shape, border, or thickness.
• Bleeding without clear trauma.
• Pain, ulceration, or persistent crusting.
• Intense itching or repeated inflammation.
• Very dark or irregular lesion.
• An injury that looks different from all the others.
• Sudden appearance of many new lesions.
• Doubt between seborrheic keratosis, mole, actinic keratosis or skin cancer.
• Injury in an area of frequent friction, shaving, or repeated bleeding.
• Personal history of melanoma, skin cancer, or immunosuppression.

The sudden appearance of numerous seborrheic keratoses has been classically described as a possible «Leser-Trélat sign,» a rare and debated association with internal cancer. In practice, not every outbreak of lesions implies cancer, but it does warrant medical evaluation if the change is sudden, noticeable, and accompanied by other general symptoms.

What does a dermatologist usually do?

The dermatologist begins with a brief medical history: when it appeared, if it has changed, if it bleeds, if it hurts, if it itches, if it has been manipulated, and if there is a history of skin cancer.

The lesion is then examined visually and with dermatoscopy , a non-invasive technique that allows visualization of structures not visible to the naked eye. In seborrheic keratosis, findings such as comedo-like openings, milia-like cysts, fissures, ridges, and a cerebriform pattern may be observed. These findings are helpful but do not replace clinical judgment.

If the lesion is typical, stable, and not bothersome, observation may suffice. If it is bothersome or the patient wishes to have it removed, it can be treated in the office. If there is diagnostic uncertainty, the dermatologist may recommend a biopsy or excision for histopathological examination. Microscopic examination is the most reliable way to confirm whether a suspicious lesion is benign or corresponds to another condition.

In dark or olive skin, the specialist will also assess the risk of hyperpigmentation or hypopigmentation after treatment. This is important because some methods, such as cryotherapy, can leave more visible or persistent color changes in certain skin types.

Frequently Asked Questions

Is seborrheic keratosis cancer?

• No. Seborrheic keratosis is considered a benign, non-cancerous lesion. The important point is that some malignant lesions can resemble it. Therefore, it’s recommended to consult a doctor if it changes, bleeds, hurts, grows rapidly, or looks different from the others.

Is it contagious?

• No. It’s not an infection or a viral wart. It’s not transmitted by touching it, sharing towels, or living with someone who has it.

Why do I get more of them as I get older?

• Because age is one of the most common contributing factors. Some people develop many due to a family history. Sun exposure, friction, and individual skin characteristics can also play a role.

Can I remove it with wart products?

• It is not recommended. Seborrheic keratosis is not a viral wart. Using caustic products can cause burns, staining, scarring, or infection, and may also delay diagnosis if the lesion was not actually seborrheic keratosis.

Should the dermatologist remove all seborrheic keratoses?

• No. Many do not require treatment. They are removed if there is diagnostic uncertainty, irritation, bleeding from friction, discomfort, snagging on clothing or jewelry, or if the person wishes to remove them for aesthetic reasons.

Can it come back after removing it?

• The treated lesion may not return, but new seborrheic keratoses may appear in other areas over time. In some cases, pigmentation, a small scar, or partial recurrence may remain.

How can I tell if it’s seborrheic keratosis or melanoma?

• It can be difficult to spot at first glance, even for people accustomed to checking their skin. If a lesion is new, irregular, changes, bleeds, has multiple colors, or is clearly distinguishable from others, it should be evaluated. Dermatoscopy and, if necessary, a biopsy help differentiate between lesions.

Bibliography and sources

• Barthelmann S, Butsch F, Lang BM, Stege H, Großmann B, Schepler H, et al. Seborrheic keratosis. J Dtsch Dermatol Ges. 2023;21(3):265-277. doi:10.1111/ddg.14984. Available at: https://pubmed.ncbi.nlm.nih.gov/36892019/
• Sun MD, Halpern AC. Advances in the etiology, detection, and clinical management of seborrheic keratoses. Dermatology. 2022;238(2):205-217. doi:10.1159/000517070. Available at: https://pubmed.ncbi.nlm.nih.gov/34311463/
• Jackson JM, Alexis A, Berman B, Berson DS, Taylor S, Weiss JS. Current understanding of seborrheic keratosis: prevalence, etiology, clinical presentation, diagnosis, and management. J Drugs Dermatol. 2015;14(10):1119-1125. Available at: https://pubmed.ncbi.nlm.nih.gov/26461823/
• Braun RP, Rabinovitz HS, Krischer J, Kreusch J, Oliviero M, Naldi L, et al. Dermoscopy of pigmented seborrheic keratosis: a morphological study. Arch Dermatol. 2002;138(12):1556-1560. Available at: https://pubmed.ncbi.nlm.nih.gov/12472342/
• Minagawa A. Dermoscopy-pathology relationship in seborrheic keratosis. J Dermatol. 2017;44(5):518-524. doi:10.1111/1346-8138.13657. Available at: https://pubmed.ncbi.nlm.nih.gov/28447350/
• Carrera C, Segura S, Aguilera P, Scalvenzi M, Longo C, Barreiro A, et al. Dermoscopic clues for diagnosing melanomas that resemble seborrheic keratosis. JAMA Dermatol. 2017;153(6):544-551. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC5540029/
• Diep D, Calame A, Cohen PR. Morphologic mimickers of seborrheic keratoses: cutaneous lesions masquerading as seborrheic keratoses. Cureus. 2021;13(10):e18797. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC8575325/
• Ammad S, Licata G, Brancaccio G, Moscarella E, Argenziano G. Clinical and dermoscopic features of seborrheic keratoses according to skin types: a retrospective study. Dermatol Practice Concept. 2023;13(4):e2023253. doi:10.5826/dpc.1304a253. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC10656179/
• American Academy of Dermatology Association. Seborrheic keratoses: overview. Available at: https://www.aad.org/public/diseases/az/seborrheic-keratoses-overview
• American Academy of Dermatology Association. Seborrheic keratoses: diagnosis and treatment. Available at: https://www.aad.org/public/diseases/az/seborrheic-keratoses-treatment
• British Association of Dermatologists. Seborrhoeic keratosis: patient information leaflet. Available at: https://www.bad.org.uk/pils/seborrhoeic-keratosis
• DermNet NZ. Seborrhoeic keratosis. Available at: https://dermnetnz.org/topics/seborrhoeic-keratosis