Skin tags grow when the body produces extra cells in the skin’s top layers, forming small, soft pouches of collagen fibers and blood vessels wrapped in skin. The triggers behind this overgrowth range from simple physical friction to deeper metabolic signals like elevated insulin levels. Most people will develop at least a few by middle age, with prevalence climbing to around 59% by the time people reach their 50s.
How a Skin Tag Actually Forms
A skin tag is structurally simple: loosely arranged collagen fibers and blood vessels surrounded by a layer of skin that can be either thickened or thinned out. They typically hang from a narrow stalk, which is why they feel soft and movable when you brush against them. They’re not tumors, cysts, or warts, though they can sometimes be confused with all three.
The process starts when something stimulates fibroblasts (the cells that produce collagen) and keratinocytes (the cells that make up the outer layer of skin) to multiply faster than normal. What triggers that stimulation varies from person to person, and often multiple factors overlap.
Friction Is the Most Common Trigger
Skin tags cluster in places where skin rubs against itself or against clothing: the armpits, neck, eyelids, groin, inner thighs, under the breasts, and around the genitals. This isn’t a coincidence. Repetitive friction irritates the skin’s surface and appears to drive the extra cell production that creates tags. People who wear tight collars, necklaces, or bras that dig in often notice tags forming along those contact lines.
This is also why skin tags are more common in people carrying extra weight. More skin folds mean more friction zones. Research published in the Journal of Clinical and Aesthetic Dermatology found that people who were overweight had a 4.7-fold higher likelihood of developing multiple skin tags compared to those at a normal weight. For people with obesity, the risk was 2.8-fold higher.
Insulin Resistance and Metabolic Health
Friction explains where skin tags appear, but it doesn’t fully explain why some people get dozens while others get none. One of the strongest internal drivers is insulin resistance, a condition where the body needs to produce more and more insulin to keep blood sugar in check.
When insulin levels stay chronically high, the excess insulin activates receptors for a growth factor called IGF-1 on the surface of fibroblasts and skin cells. This directly stimulates those cells to multiply, essentially giving them a growth signal they wouldn’t normally receive. It’s the same mechanism behind acanthosis nigricans, the velvety dark patches that sometimes appear on the neck or armpits alongside skin tags. Both conditions are outward signs that the body is struggling to manage insulin.
This connection means that a sudden crop of new skin tags, especially alongside darkened skin in the folds of the neck or armpits, can be an early visible marker of prediabetes or metabolic syndrome. Elevated cholesterol has also been linked to higher skin tag counts, though the association with triglycerides weakens when researchers control for other metabolic factors.
Hormonal Changes During Pregnancy
Many women notice new skin tags appearing during pregnancy, particularly in the second and third trimesters. The hormonal shifts involved, including surges in estrogen, progesterone, and various growth factors, create conditions that favor skin cell proliferation. Weight gain during pregnancy adds new friction zones, compounding the effect. Hormonal birth control can produce similar changes on a smaller scale. Some pregnancy-related skin tags shrink or fall off after delivery as hormone levels normalize, though many persist.
A Possible Role for HPV
A less well-known factor is the human papillomavirus. Skin tags are not warts, and for years they were considered completely unrelated to HPV. But when researchers tested skin tag tissue for viral DNA, they found HPV strains 6 and 11 in a surprisingly large percentage of samples. One study found HPV DNA in about 49% of skin tags tested, while an earlier study in a different population detected it in 88%. Crucially, the normal skin surrounding those same tags tested negative for the virus.
This doesn’t mean HPV causes skin tags the way it causes warts. The current thinking is that HPV and mechanical friction may act as cofactors, with the virus contributing to the skin cell overgrowth in areas already irritated by rubbing. Not all skin tags contain HPV, so it’s clearly not the only explanation, but it does appear to play a role in a significant portion of cases.
Genetics and Family History
If your parents had skin tags, you’re more likely to develop them too. A clear familial pattern exists, though researchers haven’t pinpointed specific genes responsible. This genetic predisposition likely influences how your skin responds to friction, how sensitive your cells are to insulin and growth factors, and how readily your fibroblasts produce excess collagen. Some people simply have skin that’s more prone to forming these growths regardless of other risk factors.
Age Is the Biggest Predictor
Skin tags are rare in children and become progressively more common with each decade of life. Prevalence climbs from about 11% in younger adults to around 59% by the 50s, then plateaus. After 50, the rate holds relatively steady through the 60s and 70s. This age-related increase tracks with the gradual accumulation of other risk factors: decades of friction, age-related insulin resistance, weight gain, and hormonal shifts through menopause or andropause.
The practical takeaway is that skin tags are almost always harmless, and their causes are largely the same forces acting on your skin over time. The factors you can influence, like maintaining a healthy weight and keeping insulin levels in check, overlap significantly with the factors that reduce your risk of developing new ones.