Mr. Onur Gilleard
Qualifications & Experience
Mr Onur Gilleard is a distinguished consultant plastic surgeon on the GMC specialist register. He previously held an NHS consultant post at St Bartholomew’s Hospital in London, specialising in skin cancer and microsurgical reconstruction. In 2021, Mr Gilleard transitioned from the NHS to dedicate himself fully to private practice, allowing him to focus exclusively on providing personalised, high-quality care to his patients. He is recognised as an expert in laser treatments, having conducted research and developed advanced treatment protocols using cutting-edge laser technology to optimise both clinical outcomes and cosmetic results.
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Seborrheic keratoses appear mainly with age and a genetic tendency, which is why they are common from around 40 onwards and often run in families. They are not your fault: they are not caused by a virus, by poor hygiene, or by anything you did, and they are not contagious. They often seem to appear “suddenly” simply because you notice one that has been forming for a while. The one situation worth a doctor’s review is a sudden crop of many at once. Here is what actually causes them, what does not, and when to get a growth checked.
What Actually Causes Them
A seborrheic keratosis forms when the surface skin cells (keratinocytes) multiply and build up into a benign, raised growth. The main drivers are:
- Age: they become much more common from around 40, which is why they are nicknamed “age warts”.
- Genetics: a tendency to develop them often runs in families, so if a parent had many, you may too.
- Skin friction and sun exposure are thought to play a part for some people, though the genetic and age factors are the dominant ones.
They are entirely benign; the full background is in our complete guide to seborrheic keratosis.
What Does Not Cause Them
It is just as useful to clear up the myths:
- Not a virus, and not a true wart. Despite the “age wart” nickname, they are not caused by HPV and are not contagious, so you cannot pass them to anyone or catch them.
- Not poor hygiene. They have nothing to do with cleanliness.
- Not something you did. No diet, product or habit causes them; they are largely down to age and genes.
Why So Many, or So Suddenly?
The honest mechanics of “suddenly”: in clinic, almost every “it appeared overnight” lesion turns out to have been present for months — SKs grow at the speed of shedding keratin, which is to say slowly. What changes suddenly is noticing: a lesion crosses a size threshold, gets irritated and darkens, or a partner spots it. Genuinely eruptive crops exist but are the rare exception, discussed below.
The one “sudden” pattern that earns a doctor’s visit
A truly abrupt eruption of many new SKs — dozens within weeks, classically itchy — is the rare Leser-Trélat phenomenon, which can accompany internal illness and deserves a medical review rather than a cosmetic appointment. The key distinction is tempo: gradual accumulation over months and years is normal SK biology; an explosive, itching crop is the outlier. Our identification guide covers it in context — and covers why panic is almost never the right response.
Most people develop more seborrheic keratoses gradually as they get older, and a single new one is completely normal. A growth can seem to appear “out of nowhere” when in fact it has been developing slowly and you have only just noticed it. There is one pattern worth knowing about: the sudden eruption of many seborrheic keratoses at once (the sign of Leser-Trélat) is uncommon and should be reviewed by a doctor, because rarely it can be linked to an internal health problem. A handful appearing over months is not this; a sudden crop in a short time is.
When to Get One Checked
Because a seborrheic keratosis can look like a melanoma, have any growth checked if it is new and changing, asymmetrical, has more than one colour, is bleeding or itching, or simply worries you. A consultant can confirm the diagnosis quickly, usually with dermoscopy; the comparison is in seborrheic keratosis vs melanoma. If a growth is confirmed benign and you would like it removed, the options are in the best treatment for seborrheic keratosis.
The “Where Did These Come From?” Threads
“I’m 34 and found five in a year. The internet says these are for 60-year-olds.”
The internet is a decade out of date. SKs commonly begin in the 30s and 40s — family history loads the dice heavily — and an early start predicts earlier accumulation, not disease. Our young-adults guide is written for exactly this discovery.
“They multiplied after a stressful year. Did stress cause them?”
Stress makes poor skin its scapegoat, but the evidence points elsewhere: genetics and accumulated years drive SKs, and a hard year mostly changes how often you look in the mirror. The lesions that “appeared” during it were almost certainly en route regardless.
“New ones keep appearing where my leggings rub. Coincidence?”
Partly not — friction does not create SKs, but it irritates, darkens and draws attention to lesions in rub zones, and chronically irritated skin showcases them sooner. The waistband is not causing your SKs; it is curating the exhibition.
Common Questions
- Why did I suddenly get a seborrheic keratosis?
- They appear mainly with age and a genetic tendency, so they become common from around 40 and often run in families. One can seem sudden when it has actually been forming slowly. They are not caused by a virus, hygiene or anything you did.
- Are they contagious?
- No. Despite the “age wart” nickname, a seborrheic keratosis is not a true wart and is not caused by a virus, so you cannot catch it or pass it on.
- Is it bad if lots appear at once?
- A few appearing over time is normal, but a sudden crop of many at once should be reviewed by a doctor, as rarely it can be linked to an internal health problem.
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