Skin tags form under your armpits primarily because of friction. The armpit is a warm, moist area where skin constantly rubs against itself and against clothing, and that repeated irritation is the single biggest trigger for these small, soft growths. But friction alone doesn’t explain why some people get dozens while others never get one. Insulin levels, hormones, weight, and genetics all play a role.
How Friction Triggers Skin Tags
Skin tags (the medical term is acrochordons) are small flaps of tissue that hang from the skin’s surface by a thin stalk. They typically range from one to five millimeters, though some grow up to two centimeters. Under a microscope, they’re made of loosely arranged collagen fibers, dilated blood vessels, and an overgrown outer skin layer. They’re not cancerous and don’t become cancerous.
Your armpits are one of the body’s most friction-heavy zones. Every time you swing your arms, raise them overhead, or simply walk, skin folds in the underarm area slide against each other. Clothing seams and bra straps add to the irritation. Over time, that chronic rubbing stimulates the skin to produce extra collagen and tissue, which bunches up into the characteristic soft pouch on a stalk. The same process explains why skin tags cluster in other high-friction spots: the neck, under the breasts, the groin, and the eyelids.
Insulin Resistance and Metabolic Health
If you’ve noticed a sudden crop of skin tags, it may be worth paying attention to your metabolic health. There’s a well-documented link between skin tags and insulin resistance, the condition where your body produces more and more insulin because cells stop responding to it efficiently. That excess insulin activates growth receptors (specifically IGF-1 receptors) on the cells that make up your skin’s connective tissue, causing them to multiply faster than normal. The result is accelerated tissue growth in areas already prone to irritation.
People with metabolic syndrome, prediabetes, or type 2 diabetes are significantly more likely to develop skin tags. In clinical settings, a cluster of skin tags is sometimes treated as a visible early warning sign that blood sugar regulation may be off. This doesn’t mean that everyone with a skin tag has a blood sugar problem, but if you’re developing many of them and you also carry extra weight around your midsection, it’s a pattern worth discussing with your doctor.
Hormonal Changes During Pregnancy
Many women notice new skin tags appearing during pregnancy, and the reason is hormonal. Skin cells have estrogen receptors, and the sharp rise in estrogen during pregnancy stimulates changes throughout the skin. Some of these changes are cosmetic and temporary, like darkened pigmentation along the belly. Others, like skin tags, tend to stick around after delivery.
Birth control pills can produce a similar, milder effect because they also raise circulating estrogen levels. Hormonal shifts during perimenopause may contribute as well, though the evidence there is less direct.
Weight, Age, and Genetics
Carrying extra body weight increases both friction and insulin levels, making it one of the strongest predictors of skin tag development. Heavier individuals tend to have deeper, moister skin folds, and obesity is closely tied to the insulin resistance pathway described above. These two mechanisms reinforce each other.
Age matters too. Skin tags are rare in children and become increasingly common after 40, likely because of cumulative friction exposure and the metabolic changes that come with aging. There also appears to be a genetic component. The exact genes haven’t been pinpointed, but skin tags tend to run in families, suggesting that some people inherit skin that’s simply more reactive to friction and growth signals.
Skin Tags vs. Warts and Moles
Before you assume a bump under your arm is a skin tag, it helps to know what else it could be. Skin tags are soft, flesh-colored or slightly darker, and dangle from a narrow stalk. They move freely when you touch them and don’t hurt unless something snags on them.
- Warts are caused by HPV and tend to be firm, rough-surfaced, and rooted directly into the skin without a stalk. One type, the filiform wart, can look elongated and stalk-like enough to be confused with a skin tag, but it usually has a rougher texture.
- Moles are flat or slightly raised, usually round and symmetrical, and feel firmly attached to the skin rather than hanging off it. A mole that changes shape, color, or size warrants medical evaluation.
If a growth is hard, painful, rapidly changing, or bleeding on its own, it’s not a typical skin tag and should be looked at by a dermatologist.
How Skin Tags Are Removed
Skin tags are harmless, so removal is purely cosmetic or comfort-related. A dermatologist can clip a small skin tag off in seconds with sterile scissors, freeze it with liquid nitrogen, or use a small electrical current to destroy the tissue. None of these procedures typically require anesthesia for very small tags, though a numbing injection is sometimes used for larger ones. Healing is straightforward: clean the area with soap and water twice a day, apply a thin layer of petroleum jelly, cover with a nonstick bandage, and avoid hydrogen peroxide or alcohol, which slow healing.
Removing skin tags at home is a different story. Skin tags are vascular, meaning they have their own blood supply and sometimes contain nerve fibers. Cutting one off with scissors or tying it with string risks uncontrolled bleeding, infection, and scarring. Over-the-counter freezing kits are less dangerous but also less precise than what a dermatologist uses, and they can damage surrounding healthy skin. The safest approach for any skin tag you want gone is professional removal, which is quick, inexpensive, and heals cleanly.
Reducing Your Risk
You can’t eliminate every factor, especially genetics and age, but you can address the biggest modifiable ones. Keeping your underarm area dry with moisture-wicking fabrics or absorbent powder reduces the friction and dampness that encourage skin tag formation. Wearing looser-fitting sleeves helps too. If you’re carrying extra weight, even modest weight loss can reduce both mechanical friction and circulating insulin levels, addressing two root causes at once.
For people already managing insulin resistance or prediabetes, improving blood sugar control through diet, exercise, or medication may slow the rate at which new skin tags appear. Existing skin tags won’t shrink or fall off on their own from lifestyle changes, but you may notice fewer new ones forming over time.