Seborrheic keratosis is one of the most common benign skin growths that typically appears as people age. Often referred to as “skin barnacles” due to their appearance, these harmless lesions affect millions of people worldwide. While they pose no serious health risks, understanding their symptoms can help you distinguish them from other skin conditions and provide peace of mind. This comprehensive guide will walk you through the most common signs and symptoms of seborrheic keratosis, helping you recognize these distinctive skin growths.
These growths can appear anywhere on the body except the palms and soles, and while they’re completely harmless, many people choose to have them evaluated or removed for cosmetic reasons. Recognizing the characteristic features of seborrheic keratoses can help you identify them early and understand what to expect as they develop.
1. Waxy or Scaly Appearance
One of the most distinctive features of seborrheic keratosis is its characteristic waxy or scaly texture. These growths often look as though they have been pasted or stuck onto the skin surface rather than growing from within it. The surface texture can vary significantly from one lesion to another.
The waxy appearance gives the growth a somewhat greasy or “painted-on” look that’s unique to this condition. When you examine a seborrheic keratosis closely, you’ll notice that the surface may have a rough, bumpy texture similar to a wart. Some lesions develop a crusty or flaky coating that can occasionally peel off, though the growth itself remains intact underneath.
This scaly texture often becomes more pronounced as the lesion matures and grows larger over time. The waxy quality is due to the accumulation of keratin, a protein that’s naturally found in skin, hair, and nails. This buildup creates the characteristic raised, textured appearance that makes seborrheic keratoses easily identifiable to dermatologists.
2. Raised, Elevated Growth
Seborrheic keratoses typically present as raised bumps or growths that stand out from the surrounding skin surface. Unlike flat moles or freckles, these lesions have a three-dimensional quality that you can both see and feel when you run your finger across them.
The elevation can range from slightly raised to quite prominent, with some growths protruding several millimeters above the skin surface. Early stage seborrheic keratoses may start out relatively flat but gradually become more elevated as they develop. This raised characteristic is one of the key features that distinguishes them from other benign skin conditions.
The degree of elevation often varies depending on the location on the body and how long the growth has been present. Lesions on areas subject to frequent friction, such as under clothing straps or around the waistline, may become more pronounced over time. The raised nature of these growths is also why they sometimes catch on clothing or jewelry, which can cause irritation or minor bleeding.
3. Brown, Black, or Tan Coloration
The color of seborrheic keratoses is another telltale sign of this condition. These growths most commonly appear in shades of brown, ranging from light tan to dark brown or even black. The pigmentation comes from melanin, the same substance that gives skin its color.
The color intensity can vary significantly from person to person and even between different lesions on the same individual. Some people develop light tan growths that barely contrast with their natural skin tone, while others may have very dark brown or black lesions that are highly visible. It’s not uncommon for a single seborrheic keratosis to display multiple shades of brown within the same growth.
In some cases, seborrheic keratoses may appear pink, red, or skin-colored, particularly in people with lighter complexions. The color typically remains stable over time, though some lesions may gradually darken as they age. This wide range of coloration is normal and doesn’t indicate any cause for concern. However, if you notice a rapid change in color or if a growth becomes inflamed and red, it’s advisable to have it evaluated by a healthcare professional.
4. Well-Defined, Round or Oval Shape
Seborrheic keratoses characteristically have well-defined borders with a clearly demarcated edge that separates them from the surrounding healthy skin. The shape is typically round or oval, though some lesions may have slightly irregular borders.
The distinct border is an important diagnostic feature that helps differentiate seborrheic keratoses from other skin conditions. Unlike some skin cancers that may have fuzzy or poorly defined edges, these benign growths maintain a clear boundary that makes them easy to distinguish from the adjacent skin. The edge may appear somewhat sharp, as if the growth has been carefully outlined.
The size of these lesions can vary considerably, ranging from a few millimeters to several centimeters in diameter. Most seborrheic keratoses measure between 0.2 to 3 centimeters across. While they maintain their round or oval shape, larger lesions may occasionally develop a more irregular contour. The well-defined nature of these growths remains consistent regardless of their size, making this feature a reliable identifying characteristic throughout all stages of development.
5. “Stuck-On” or Pasted Appearance
Perhaps one of the most characteristic and distinctive features of seborrheic keratosis is its “stuck-on” appearance. Dermatologists frequently use this term because these growths genuinely look as though someone has attached a small piece of material to the skin surface with glue.
This unique appearance results from the way seborrheic keratoses develop. Unlike growths that originate deep within the skin layers, these lesions form primarily in the epidermis, the outermost layer of skin. This superficial development gives them their characteristic flat-bottomed appearance with a clear demarcation between the growth and the underlying skin.
The stuck-on quality becomes more apparent as the lesion matures. When viewed from the side, you can often see a clear line where the growth meets the normal skin, similar to looking at the edge of a sticker on a smooth surface. This feature is so distinctive that experienced dermatologists can often diagnose seborrheic keratosis simply by visual examination. The pasted-on appearance also explains why some removal techniques can effectively lift off these growths with minimal depth of treatment.
6. Multiple Growths in Various Locations
While it’s possible to have just one seborrheic keratosis, most people who develop these growths will eventually have multiple lesions scattered across different areas of their body. This multiplicity is a common pattern and becomes more prevalent with advancing age.
The growths can appear virtually anywhere on the body except for the palms of the hands and soles of the feet, which typically remain unaffected. Common locations include the face, chest, shoulders, back, and scalp. Some people develop just a handful of lesions, while others may have dozens or even hundreds of seborrheic keratoses over their lifetime.
The distribution pattern is usually random, though there may be some clustering in sun-exposed areas. Family members often show similar patterns of seborrheic keratosis development, suggesting a genetic component to their occurrence. Having multiple growths doesn’t indicate any increased health risk—it’s simply part of the natural variation in how these benign lesions manifest. Each growth typically develops independently and may appear at different times throughout adulthood.
7. Slow Growth with Occasional Itching or Irritation
Seborrheic keratoses typically grow very slowly over months or years. In their early stages, they may be barely noticeable, starting as small, flat spots that gradually become more raised and prominent over time. This slow progression is normal and expected with these benign growths.
While seborrheic keratoses are generally asymptomatic, meaning they don’t cause discomfort, some people experience occasional itching or irritation, particularly if the growth is located in an area that experiences friction from clothing or jewelry. The itching is usually mild and intermittent rather than constant or severe.
Irritation can occur when lesions are repeatedly rubbed or scratched, which may cause the surface to become inflamed or even bleed slightly. Growths located on the scalp may become irritated during hair brushing or combing. Those on the torso might be affected by tight clothing or bra straps. While this irritation is generally minor, it’s one of the reasons some people choose to have these growths removed. If a seborrheic keratosis becomes persistently painful, bleeds without trauma, or shows signs of infection such as increased redness, warmth, or discharge, it’s important to have it evaluated by a healthcare provider to rule out other conditions.
Main Causes of Seborrheic Keratosis
While the exact cause of seborrheic keratosis remains not fully understood, several factors have been identified as contributing to their development:
Age and Natural Skin Aging: The most significant factor in developing seborrheic keratoses is advancing age. These growths are extremely rare in people under 30 and become increasingly common after age 40. By age 60, more than half of adults have at least one seborrheic keratosis. The accumulation of years of skin cell turnover appears to play a crucial role in their formation.
Genetic Predisposition: Heredity plays a substantial role in seborrheic keratosis development. If your parents or siblings have these growths, you’re more likely to develop them as well. The condition often runs in families, with similar patterns of occurrence across generations. Some families show a tendency toward developing numerous lesions, while others may have only a few scattered growths.
Sun Exposure: While seborrheic keratoses can appear on both sun-exposed and covered areas of the body, there’s evidence suggesting that cumulative sun exposure over a lifetime may contribute to their development. However, unlike skin cancers, the relationship with sun exposure is less direct and clear-cut. These growths are not considered sun damage in the same way that actinic keratoses or skin cancers are.
Skin Type and Complexion: Seborrheic keratoses can affect people of all skin types and ethnicities, though their appearance may vary. People with darker skin tones may develop lesions that appear differently than those seen in lighter-skinned individuals. The condition is common across all racial and ethnic groups.
Human Papillomavirus (HPV): Some research has suggested a possible link between certain strains of HPV and seborrheic keratosis development, though this connection remains under investigation and is not definitively established. The role of viral factors in these growths is still being studied by researchers.
Frequently Asked Questions
Are seborrheic keratoses cancerous or dangerous?
No, seborrheic keratoses are completely benign (non-cancerous) growths. They do not turn into cancer and pose no health risk. However, because they can sometimes resemble skin cancer, it’s important to have any new or changing skin growth evaluated by a healthcare provider to ensure proper diagnosis.
Can seborrheic keratosis spread from person to person?
No, seborrheic keratoses are not contagious and cannot spread from one person to another through contact. They develop due to internal factors such as genetics and aging rather than from any infectious agent.
Will seborrheic keratosis go away on its own?
Seborrheic keratoses typically do not disappear without treatment. Once they develop, they usually remain permanently unless removed. In rare cases, a lesion may become irritated and fall off, but this is uncommon. Most growths remain stable or slowly increase in size over time.
How can I tell the difference between seborrheic keratosis and skin cancer?
While seborrheic keratoses have distinctive “stuck-on” appearance, waxy texture, and well-defined borders, it can be difficult for non-professionals to distinguish them from certain skin cancers, particularly melanoma. Any new growth, or existing growth that changes in size, shape, color, or begins to bleed, should be evaluated by a dermatologist or healthcare provider.
At what age do seborrheic keratoses typically appear?
Seborrheic keratoses most commonly begin appearing after age 40, with prevalence increasing significantly with advancing age. They’re sometimes called “wisdom spots” because they’re associated with aging. However, some people may develop them earlier, particularly if there’s a strong family history.
Can seborrheic keratosis develop on any part of the body?
Seborrheic keratoses can develop almost anywhere on the body except for the palms of the hands and soles of the feet. They most commonly appear on the face, chest, shoulders, back, and scalp, but can occur on the arms, legs, and other areas as well.
Do seborrheic keratoses require treatment?
Since seborrheic keratoses are benign, treatment is not medically necessary. However, many people choose to have them removed for cosmetic reasons or if they become irritated by clothing or jewelry. If you’re considering removal, consult with a dermatologist to discuss appropriate options for your specific situation.
Why do I suddenly have many seborrheic keratoses appearing?
The sudden appearance of multiple seborrheic keratoses, known as the “sign of Leser-Trélat,” can occasionally be associated with internal malignancy, though this is rare. If you notice many new growths appearing rapidly, it’s advisable to consult with a healthcare provider for proper evaluation, even though most cases are simply age-related and benign.
References:
- American Academy of Dermatology – Seborrheic Keratoses
- Mayo Clinic – Seborrheic Keratosis
- NHS – Seborrhoeic Keratoses
- DermNet NZ – Seborrhoeic Keratosis
- National Center for Biotechnology Information – Seborrheic Keratosis
The information on this page is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions related to your health.
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