Skin tags under the arms are primarily caused by repeated skin-on-skin friction in the armpit fold, combined with other factors like weight, hormonal changes, and metabolic health. They’re extremely common: roughly 30% of adults have at least one, and the armpit is one of the most frequent locations. These small, soft, flesh-colored growths are completely benign, but understanding why they form can help you reduce new ones and recognize when they might signal something worth paying attention to.
Why Armpits Are a Hot Spot
Skin tags form when the body produces extra cells in the top layers of skin. Structurally, they’re made up of loosely arranged collagen fibers and tiny blood vessels, covered by a thickened outer skin layer. They grow on a narrow stalk that connects them to the skin’s surface, which is why they tend to dangle or wobble when touched.
The armpit is one of the body’s most active friction zones. Every time you move your arms, the skin folds against itself. That constant rubbing irritates the surface and stimulates cell overgrowth in the area. This is why skin tags cluster in places where skin meets skin: armpits, the neck, under the breasts, the groin, and along the eyelids. Tight clothing, bra straps, and jewelry that press against the underarm area add to the mechanical irritation, giving the skin even more reason to build up extra tissue.
Weight, Insulin, and Metabolic Health
Carrying extra body weight increases the number and depth of skin folds, which creates more friction. But the connection goes deeper than mechanics. A cross-sectional study comparing 100 people with skin tags to 100 matched controls found that 65% of those with skin tags met the criteria for metabolic syndrome, compared to just 28% of controls. Metabolic syndrome is a cluster of conditions including elevated blood sugar, high blood pressure, and abnormal cholesterol levels that often travel together and raise the risk of type 2 diabetes and heart disease.
The link to blood sugar is particularly strong. Elevated fasting glucose was significantly associated with skin tags in the study. Insulin resistance, the underlying driver of type 2 diabetes, appears to fuel skin tag growth by promoting cell proliferation in the skin. If you’ve noticed a sudden increase in skin tags, especially in multiple body areas, it may be worth having your blood sugar and metabolic markers checked. Notably, people whose skin tags were limited to the armpits alone were less likely to have metabolic syndrome than those with tags on multiple body sites.
Hormonal Changes
Pregnancy is a well-known trigger for new skin tags. The hormonal shifts that occur during pregnancy, particularly increases in estrogen and growth factors, can stimulate the skin to produce extra tissue. These tags typically don’t go away after delivery, though they can be removed cosmetically afterward. Birth control pills can produce similar effects, since they work by altering the same hormonal pathways. Hormonal changes during menopause and normal aging also contribute, which is why skin tags become more common with age.
A Possible Viral Connection
Some researchers have investigated whether certain strains of human papillomavirus (HPV) play a role. One study found low-risk HPV strains in about 71% of skin tag samples, compared to only 13% of nearby normal skin. However, other studies have found no HPV in skin tags at all. The relationship remains unclear and contradictory across research. HPV may be a contributing factor in some cases, but friction and metabolic issues are far more consistently supported as causes.
Skin Tags vs. Warts vs. Moles
It’s easy to confuse a skin tag with a wart or mole, especially in the armpit where it’s hard to get a good look. Here’s how to tell them apart:
- Skin tags are soft, smooth, and hang from the skin on a thin stalk. They compress easily when you press them. Most are 1 to 5 millimeters, though some reach 1 to 2 centimeters.
- Warts are firmer bumps that sit flat against the skin or rise only slightly. Their surface feels rough or bumpy, sometimes described as cauliflower-like. They can itch or bleed.
- Moles are typically flat or slightly raised, with a uniform round shape and darker pigmentation. They don’t dangle on a stalk.
If a growth under your arm is hard, rough-textured, rapidly changing in color, or bleeding without being snagged, it’s worth having it examined.
Reducing New Skin Tags
You can’t always prevent skin tags, but you can reduce the conditions that encourage them. Keeping the underarm area dry and minimizing friction helps. Loose-fitting clothing and avoiding tight sleeves or accessories that press into the armpit reduce mechanical irritation. If excess weight is a factor, even modest weight loss can decrease the depth of skin folds and lower insulin resistance, both of which reduce the stimulus for new tags to form.
Existing skin tags don’t need to be removed unless they’re bothering you. Friction from clothing or movement can sometimes cause them to twist, snag, or bleed, which is the most common reason people seek removal. A doctor can remove them quickly through freezing, cutting, or cauterizing, all of which are minor office procedures. Pulling or cutting them off yourself risks infection and scarring.