Seborrheic Keratosis: Causes, Symptoms & Removal

What Is Seborrheic Keratosis?

Seborrheic keratosis is a common, harmless skin growth that appears as a raised, waxy, or scaly bump. These growths are benign (non-cancerous), do not spread, and never develop into skin cancer. They are sometimes called seborrheic warts or senile warts, though they are not true warts and are not caused by any virus.

Seborrheic keratoses are among the most common benign skin tumors, affecting the vast majority of middle-aged and older adults. The name "seborrheic" refers to their waxy, greasy appearance, while "keratosis" indicates a growth of keratin, the protein that makes up the outer layer of skin. Despite the somewhat alarming terminology, these growths are entirely harmless from a medical perspective.

The appearance of seborrheic keratoses can vary significantly from person to person and even from one growth to another on the same individual. They typically have a characteristic "stuck-on" appearance, as if a piece of brown or tan wax was dripped onto the skin and hardened. This distinctive look often helps distinguish them from other types of skin lesions, including potentially dangerous ones like melanoma.

While seborrheic keratoses can appear on almost any part of the body, they are most common on areas that have been exposed to the sun over many years, including the face, chest, shoulders, and back. They rarely appear on the palms of the hands, soles of the feet, or mucous membranes. The growths develop in the upper layer of the skin (epidermis) and do not extend deeper into underlying tissues.

Why Do Seborrheic Keratoses Develop?

The exact cause of seborrheic keratoses remains incompletely understood, though researchers have identified several contributing factors. Age is the most significant risk factor, with the vast majority of people developing at least one seborrheic keratosis by the time they reach 60 years of age. This strong association with aging suggests that accumulated changes to skin cells over time play a key role.

Genetic factors clearly influence susceptibility to seborrheic keratoses. Studies show that people with a family history of multiple seborrheic keratoses are more likely to develop them themselves, and certain genetic variations have been associated with increased risk. The condition appears to run in families, with some individuals developing many growths while others develop only a few.

Sun exposure may contribute to the development of seborrheic keratoses on sun-exposed skin, though the relationship is less direct than with other skin conditions like actinic keratosis or skin cancer. Some studies suggest that ultraviolet light exposure may trigger or accelerate the formation of these growths in genetically susceptible individuals, which would explain their preference for areas like the face, chest, and back.

What Are the Symptoms of Seborrheic Keratosis?

Seborrheic keratoses appear as raised, round or oval growths with a waxy, scaly, or rough surface. They range in color from light tan to dark brown or black, and typically measure between 5 millimeters and 5 centimeters. Most cause no symptoms, though some may itch or become irritated from rubbing against clothing.

The appearance of seborrheic keratoses is quite distinctive, making them recognizable to experienced healthcare providers in most cases. The growths typically start small and gradually enlarge over months to years. Their surface texture can range from smooth and waxy in early stages to rough, crusty, or warty as they mature. The characteristic "stuck-on" appearance comes from their clear demarcation from surrounding skin.

Color variation is one of the most notable features of seborrheic keratoses. A single growth may display multiple shades ranging from white and yellow through various tans and browns to deep brown or nearly black. This color variation can sometimes cause concern, as irregular pigmentation is also a feature of melanoma. However, the colors in a seborrheic keratosis typically remain stable over time and follow predictable patterns.

While most seborrheic keratoses cause no physical symptoms, some individuals experience itching, particularly with growths located in areas subject to friction. Clothing, jewelry, or other objects rubbing against the growth can cause irritation, redness, and discomfort. In some cases, this chronic irritation may cause the keratosis to bleed or become inflamed, prompting people to seek medical evaluation.

Typical Appearance and Characteristics

Understanding the typical features of seborrheic keratoses can help distinguish them from other skin conditions. These growths characteristically have a well-defined border, meaning you can clearly see where the growth ends and normal skin begins. The surface often shows small, rough bumps or a granular texture, and many have visible tiny plugged hair follicles that give them a "warty" appearance.

The color of seborrheic keratoses reflects the amount of melanin they contain, which is why fair-skinned individuals tend to develop lighter-colored growths while those with darker skin may develop very dark brown or black ones. The entire growth typically maintains a relatively uniform color pattern, unlike melanomas, which often show irregular, patchy pigmentation with distinct areas of different colors.

Common Locations

Seborrheic keratoses show a marked preference for certain body areas. The face is a common location, with growths frequently appearing on the temples, cheeks, and forehead. The chest and back are also frequently affected, particularly in areas that receive regular sun exposure. The shoulders, scalp, and upper arms represent other common sites.

Interestingly, seborrheic keratoses rarely develop on the palms, soles, or inside the mouth. They can, however, appear almost anywhere else on the body, including the legs, arms, and trunk. Some individuals develop them predominantly in one area, while others may have them scattered across multiple body regions.

When Should You See a Doctor About Seborrheic Keratosis?

See a doctor if you are unsure whether a growth is a seborrheic keratosis, if it bleeds or changes in appearance, if it becomes infected and does not heal within several weeks, or if it causes significant irritation. While seborrheic keratoses themselves are harmless, professional evaluation ensures accurate diagnosis and rules out conditions that may look similar, including skin cancer.

Although seborrheic keratoses are benign and require no treatment from a medical standpoint, there are several compelling reasons to have a healthcare provider evaluate any new or changing skin growth. The primary concern is ensuring accurate diagnosis, as some skin cancers, particularly melanoma, can initially resemble seborrheic keratoses. Only a trained professional can reliably distinguish between these conditions.

Bleeding from a skin growth is always worth investigating. While seborrheic keratoses can bleed if they are scratched, rubbed, or caught on clothing, persistent or unexplained bleeding warrants professional evaluation. Similarly, any growth that changes rapidly in size, color, or appearance should be examined promptly, as these changes may indicate a different underlying condition.

Infection of seborrheic keratoses can occur, particularly if the growth has been scratched or injured. Signs of infection include increasing redness, warmth, swelling, pain, and sometimes discharge of pus. While minor irritation often resolves on its own, infection that persists for more than a few weeks or worsens over time requires medical attention and may need antibiotic treatment.

The Importance of Professional Diagnosis

Self-diagnosis of skin growths can be risky because several serious conditions can mimic the appearance of seborrheic keratoses, at least in their early stages. Melanoma, the most dangerous form of skin cancer, sometimes develops features that overlap with seborrheic keratosis, particularly the dark pigmentation. Pigmented basal cell carcinoma, another form of skin cancer, can also present with similar features.

Dermatologists use several techniques to evaluate skin growths and confirm diagnoses. Visual examination by an experienced clinician is often sufficient for typical seborrheic keratoses. Dermoscopy, which uses a specialized magnifying device with polarized light, allows detailed examination of skin structures that are invisible to the naked eye and helps distinguish benign from malignant lesions.

In cases where the diagnosis remains uncertain after clinical and dermoscopic examination, a skin biopsy may be recommended. This involves removing a small sample of the growth for microscopic examination by a pathologist. While biopsies are rarely needed for typical seborrheic keratoses, they provide definitive diagnosis when there is any doubt about the nature of a lesion.

How Is Seborrheic Keratosis Diagnosed?

Seborrheic keratosis is typically diagnosed through visual examination by a dermatologist, often aided by dermoscopy (magnified examination with a special device). The characteristic "stuck-on" appearance, waxy texture, and well-defined borders usually make identification straightforward. A skin biopsy is performed only when the diagnosis is uncertain or skin cancer must be ruled out.

The diagnosis of seborrheic keratosis relies primarily on clinical examination, as these growths have distinctive features that experienced healthcare providers can recognize. The classic presentation includes a well-defined, raised lesion with a waxy or scaly surface and the characteristic appearance of being "pasted on" to the skin. When these features are clearly present, the diagnosis can often be made with high confidence without any additional tests.

Dermoscopy has become an invaluable tool in dermatological diagnosis, including the evaluation of pigmented skin lesions. This technique involves examining the skin through a handheld device that provides magnification and specialized lighting, revealing structures and patterns invisible to the naked eye. For seborrheic keratoses, dermoscopy typically shows characteristic features including comedo-like openings, milia-like cysts, and fissures and ridges that help confirm the diagnosis.

The clinical history also contributes to diagnosis. Healthcare providers typically ask about how long the growth has been present, whether it has changed over time, whether similar growths exist elsewhere on the body, and whether there is a family history of seborrheic keratoses. A history of slow growth over months to years, stable appearance, and multiple similar lesions all support the diagnosis of seborrheic keratosis.

Distinguishing From Other Conditions

Several skin conditions can resemble seborrheic keratoses, and accurate differentiation is essential for appropriate management. Melanoma, though usually distinguishable by its irregular borders, multiple colors, and asymmetric shape, can occasionally be confused with very dark seborrheic keratoses. The ABCDEs of melanoma (Asymmetry, Border irregularity, Color variation, Diameter, Evolution) help guide evaluation of pigmented lesions.

Actinic keratoses are another common skin growth that may appear similar to seborrheic keratoses. However, actinic keratoses are precancerous lesions that require monitoring or treatment. They typically appear as rough, scaly patches on sun-exposed skin and lack the waxy, raised appearance characteristic of seborrheic keratoses. Differentiating between these conditions has important implications for management.

Common warts, caused by HPV infection, can sometimes resemble seborrheic keratoses, particularly when located on the trunk or extremities. However, true warts typically have a rougher surface with visible black dots (thrombosed capillaries) and lack the greasy, stuck-on appearance of seborrheic keratoses. Additionally, common warts are more frequent in younger people, while seborrheic keratoses predominantly affect older adults.

How Is Seborrheic Keratosis Treated?

Seborrheic keratoses do not require treatment for medical reasons since they are completely benign. However, removal is available for those who experience irritation or discomfort, or who dislike the appearance of their growths. Common removal methods include cryotherapy (freezing), curettage (scraping), and electrocautery (burning). These procedures are quick, usually performed in a doctor's office, and generally have good cosmetic outcomes.

Because seborrheic keratoses pose no health risk and never develop into cancer, the decision to treat them is entirely based on personal preference and comfort. Many people choose to leave their seborrheic keratoses alone, particularly those that are small, located in inconspicuous areas, or cause no symptoms. This approach is perfectly acceptable from a medical standpoint and avoids the costs and potential complications of treatment.

For those who do choose removal, several effective methods are available. The choice of treatment depends on factors including the size, location, and number of growths to be removed, as well as patient preference and the equipment available in the treating facility. Most removal procedures can be completed in a single office visit and require little to no downtime for recovery.

It is important to understand that seborrheic keratoses can recur after removal, and removing existing growths does nothing to prevent new ones from developing. People who are genetically predisposed to seborrheic keratoses will likely continue to develop new growths throughout their lives, regardless of how many are removed. This should be considered when deciding whether removal is worthwhile.

Cryotherapy (Freezing)

Cryotherapy involves applying liquid nitrogen to the seborrheic keratosis, freezing the tissue and causing the growth to die and eventually fall off. This is one of the most common and widely available treatments for seborrheic keratoses. The procedure takes only seconds per growth and usually does not require local anesthesia, though patients typically experience a brief stinging sensation during application.

After cryotherapy, the treated area typically forms a blister within a day or two, which then crusts over and heals within one to three weeks. The healing time depends on the size and location of the treated growth, with larger lesions and those on the lower legs taking longer to heal. Temporary redness, lightening, or darkening of the skin at the treatment site is common and usually fades over several months.

Curettage (Scraping)

Curettage involves scraping the seborrheic keratosis off the skin using a curette, a specialized instrument with a sharp, rounded edge. This method is particularly effective for larger or thicker growths that may not respond as well to freezing alone. Local anesthesia is usually applied before curettage to numb the area and minimize discomfort during the procedure.

The procedure creates a superficial wound that heals over one to two weeks, forming a scab that eventually falls off to reveal new skin underneath. Curettage can be combined with electrocautery (using heat to stop bleeding and destroy any remaining cells) for more complete removal and better hemostasis. The cosmetic outcome is generally good, though some scarring or pigment changes may occur.

Other Removal Methods

Electrocautery uses electrical current to heat and destroy seborrheic keratoses. This method can be used alone or in combination with curettage. Laser treatment is another option, using focused light energy to vaporize the growth. Both methods are effective but may be more expensive than cryotherapy or curettage and may not be available in all treatment settings.

Shave excision, which involves using a blade to shave the growth off at its base, is another option for protruding seborrheic keratoses. This method provides a tissue sample that can be examined microscopically if there is any question about the diagnosis. However, it typically is not needed for clearly benign lesions where the diagnosis is certain.

What Complications Can Occur?

Seborrheic keratoses themselves rarely cause complications. Occasional issues include inflammation or irritation (which may cause the growth to become sore or fall off), bleeding from trauma, and infection if the skin is broken. After removal procedures, potential complications include temporary skin discoloration, scarring, and recurrence of the growth.

The vast majority of seborrheic keratoses cause no problems whatsoever beyond their cosmetic appearance. However, certain complications can occasionally occur, either spontaneously or as a result of treatment. Understanding these potential issues helps patients know when to seek medical attention and set appropriate expectations for removal procedures.

Spontaneous inflammation of seborrheic keratoses, sometimes called "inflamed" or "irritated" seborrheic keratosis, occurs when the growth becomes red, swollen, and sometimes tender. This inflammation can be triggered by trauma, such as scratching or friction from clothing, but sometimes occurs without obvious cause. Interestingly, inflamed seborrheic keratoses often become crusted and eventually fall off on their own, essentially removing themselves.

Mechanical irritation from clothing, jewelry, or other objects is the most common day-to-day problem caused by seborrheic keratoses. Growths located in areas subject to friction may become chronically irritated, leading to discomfort and occasional bleeding. This is often the primary reason patients choose to have seborrheic keratoses removed, particularly those located on the waistline, bra line, or under jewelry.

Post-Treatment Complications

All removal methods carry some risk of complications, though serious problems are uncommon. The most frequent issue is temporary skin discoloration at the treatment site. This may manifest as hypopigmentation (lighter skin) or hyperpigmentation (darker skin) and is more noticeable in people with darker skin tones. Most discoloration improves over several months but may be permanent in some cases.

Scarring can occur after any removal procedure, though the risk is generally low when treatment is performed by experienced practitioners. The type and extent of scarring depend on factors including the treatment method used, the size and location of the growth, individual healing characteristics, and wound care after the procedure. Keeping the wound clean and protected during healing minimizes scarring risk.

Recurrence of seborrheic keratoses after removal is relatively common. The growth may return at the same site, or new seborrheic keratoses may develop in nearby areas. This does not indicate treatment failure but simply reflects the ongoing tendency to develop these growths. Patients should understand that removal provides treatment for existing growths but does not prevent future ones from developing.

Can Seborrheic Keratosis Be Prevented?

There is no proven way to prevent seborrheic keratoses from developing. They are largely determined by genetics and age, making them a normal part of skin aging for most people. Sun protection may help reduce the number of growths on sun-exposed areas, though the connection between sun exposure and seborrheic keratosis is less clear than with other skin conditions.

Unlike some skin conditions where specific preventive measures can significantly reduce risk, seborrheic keratoses cannot be reliably prevented. The strongest risk factors - age and genetic predisposition - are not modifiable. People who are genetically prone to developing seborrheic keratoses will likely continue to develop them throughout their adult lives regardless of any preventive efforts.

Some evidence suggests that cumulative sun exposure may contribute to the development of seborrheic keratoses on sun-exposed skin. For this reason, practicing good sun protection throughout life may help reduce the number of growths that develop in these areas. However, the benefit is likely modest, and seborrheic keratoses can develop on sun-protected skin as well, indicating that sun exposure is only one factor among many.

While prevention is not currently possible, early recognition and monitoring of skin growths remains important. Regular self-examination of the skin helps identify new or changing growths that may need professional evaluation. People with many seborrheic keratoses should pay particular attention to any growth that looks different from their others, as this could indicate a different condition requiring attention.

What Is the Leser-Trelat Sign?

The sign of Leser-Trelat refers to the sudden appearance of multiple seborrheic keratoses over a short period, typically weeks rather than the usual months to years. While rare, this pattern has been associated with internal malignancies in some cases and warrants thorough medical evaluation to rule out underlying conditions.

In the vast majority of cases, seborrheic keratoses develop gradually over months to years and represent a normal, benign process of skin aging. However, the sudden eruption of many seborrheic keratoses within a short time frame - known as the sign of Leser-Trelat - is an unusual pattern that has been linked to internal cancers in some patients. This association, while not universal, makes rapid development of multiple seborrheic keratoses worth investigating.

The sign of Leser-Trelat was first described in the 19th century and has since been reported in association with various internal malignancies, particularly cancers of the gastrointestinal tract, lung, and breast. The exact mechanism behind this association is not fully understood, but it may involve growth factors produced by tumors that stimulate skin cell proliferation. Not all patients with the sign of Leser-Trelat have underlying cancer, and the association remains controversial among some experts.

Patients who experience a sudden eruption of multiple seborrheic keratoses, particularly if accompanied by other symptoms such as unexplained weight loss, fatigue, or changes in bowel habits, should seek medical evaluation. The workup typically includes a thorough physical examination, blood tests, and potentially imaging studies to screen for underlying conditions. Even if no abnormality is found, continued monitoring may be recommended.