Skin tags show up in your armpits because the skin there is constantly folding and rubbing against itself. That mechanical friction is the single biggest trigger, but it’s rarely the only factor. Roughly 46% of adults develop skin tags at some point, and the armpit is one of the most common locations. Understanding why they form can help you figure out whether yours are a cosmetic nuisance or a signal worth paying attention to.
Friction Is the Primary Trigger
Skin tags form when the body produces extra cells in the skin’s top layers. They tend to develop specifically in areas where natural movement causes skin to rub against itself, and your armpits check every box. Every time you swing your arms, reach overhead, or simply walk, the skin in your underarm creases and slides. Over years of this repetitive contact, small soft pouches of skin begin to protrude.
Tight clothing adds to the problem. Bra straps, fitted sleeves, and even the seams of athletic wear create additional friction right along the armpit fold. If you’ve noticed skin tags clustering along a line where a strap sits, that’s not a coincidence.
Insulin Resistance and Blood Sugar
Friction explains the location, but metabolic factors often explain the timing. One of the strongest associations researchers have found is between skin tags and insulin resistance, the condition where your cells stop responding efficiently to insulin and your body compensates by producing more of it.
When insulin levels stay elevated, the excess insulin binds to growth-factor receptors on skin cells. That binding triggers both the outer skin cells (keratinocytes) and the structural cells beneath them (fibroblasts) to multiply faster than normal. The result is small overgrowths of tissue, particularly in areas already irritated by friction. This is why a sudden increase in skin tags, especially if you’re also noticing darkened skin in your neck creases or armpits, can be an early visible sign of prediabetes or type 2 diabetes before blood sugar numbers look alarming on a standard test.
Weight and Leptin
Carrying extra weight contributes in two ways. The obvious one is more skin-on-skin contact: larger skin folds mean more friction surfaces. The less obvious mechanism involves a hormone called leptin, a protein released by fat tissue that helps regulate body weight and metabolism.
Research published in the Indian Journal of Dermatology, Venereology and Leprology found significantly elevated leptin levels inside skin tag tissue itself. Leptin promotes the growth of new blood vessels and stimulates skin cells to proliferate, both of which are needed to build a skin tag from scratch. Because leptin levels rise with obesity, diabetes, and pregnancy, this hormone may be a shared thread connecting all three of those conditions to skin tag development.
Hormonal Changes During Pregnancy
If your armpit skin tags appeared during pregnancy, hormones are the likely explanation. Pregnancy raises levels of estrogen, progesterone, and several growth factors while also increasing leptin output and shifting how your body handles insulin. Many women notice new skin tags during the second and third trimesters, particularly in the armpits, under the breasts, and along the neck. Some of these shrink or fall off after delivery as hormone levels normalize, though not all of them do.
Genetics Play a Role
Some people are simply more prone to skin tags than others. If one or both of your parents developed them, your likelihood goes up. The specific genetic markers haven’t been pinpointed yet, but the family clustering pattern is consistent enough that dermatologists consider it a recognized risk factor. This also explains why some thin, metabolically healthy people still get armpit skin tags: their skin may just be wired to overreact to friction.
Age Makes Them More Common
Skin tags become increasingly common from your 30s onward and peak in middle age. The longer your skin has been subjected to repeated folding and rubbing, the more opportunities those extra cells have to accumulate. Aging skin also loses some of its elasticity, creating looser folds that generate more friction. If you’re noticing your first armpit skin tags in your 40s or 50s, age alone could be a sufficient explanation.
How to Tell It’s Actually a Skin Tag
A skin tag is a soft, flesh-colored flap that hangs from the skin by a thin stalk. It’s usually small, between 1 and 5 millimeters, though some grow larger. They’re painless unless something catches on them. A few other growths can look similar but aren’t the same thing.
- Seborrheic keratoses are waxy, brown or black spots that look like they’ve been stuck onto the skin’s surface. They’re flat or slightly raised and don’t hang from a stalk.
- Warts tend to have a rough, bumpy texture and are caused by a virus. They’re usually firmer than skin tags and sit flush against the skin.
- Moles are typically flat or dome-shaped with a uniform color. A mole that changes shape, color, or size warrants a closer look.
If a growth in your armpit is hard, painful, rapidly changing, or a different color than your surrounding skin, it’s worth having a dermatologist examine it rather than assuming it’s a skin tag.
Removal Options
Skin tags are benign. They don’t become cancerous and don’t need to be removed for medical reasons. But if they’re bothering you, catching on clothing, or you simply don’t want them there, a dermatologist can remove them in a quick office visit using one of three standard approaches.
Cryotherapy involves applying liquid nitrogen to freeze the tag. A small blister or scab forms and falls off within a week or two, taking the skin tag with it. Electrodesiccation uses a tiny needle to deliver an electrical current that destroys the tissue; the resulting scab heals in one to three weeks. Snip excision is the most straightforward: the area is numbed, and the tag is cut off with sterile scissors or a blade. All three methods work well for small to medium skin tags.
Why Home Removal Can Backfire
Over-the-counter freezing kits and ligation bands are widely sold, but they carry real risks when used on sensitive armpit skin. The FDA’s adverse event database includes reports of at-home freeze kits causing burns, significant bruising that spread across the shoulder and chest, and ruptured blood vessels beneath the skin. One case required hospitalization. The armpit is particularly vulnerable because the skin is thin, sits near major blood vessels, and is prone to bacterial exposure from sweat. Tying off a skin tag with string or dental floss, a common home remedy, introduces infection risk in an area that stays warm and moist all day.
If you have a small, clearly identifiable skin tag that bothers you, professional removal is fast, inexpensive, and far less likely to leave you with a complication that’s worse than the original tag.