Skin tags in the armpits develop primarily because of friction, but the full picture involves metabolism, hormones, genetics, and body composition. These small, soft, flesh-colored growths (called acrochordons in medical literature) are extremely common in adults and almost always harmless. Understanding what drives their formation can help you make sense of why they keep appearing in this particular spot.
Why the Armpit Is a Hot Spot
Skin tags form where skin repeatedly rubs against skin or clothing, and the armpit is one of the body’s most friction-heavy zones. Every time you move your arms, the skin folds in your underarm area slide against each other. Over time, this constant mechanical irritation stimulates the outer layer of skin and the connective tissue beneath it to overgrow, forming a small stalk of tissue that hangs off the surface.
Internally, a skin tag is made up of loosely arranged collagen fibers and blood vessels surrounded by a layer of normal skin cells. It’s essentially a benign overgrowth of the same tissue that’s already there, not a viral infection or a tumor. The groin, neck, under the breasts, and eyelids are other common locations for the same reason: they’re all areas where skin folds create persistent rubbing.
Insulin Resistance and Blood Sugar
Friction alone doesn’t explain why some people develop dozens of skin tags while others develop none. One of the strongest associations researchers have found is between skin tags and insulin resistance, the metabolic state where your body’s cells don’t respond efficiently to insulin. When cells resist insulin, the pancreas compensates by producing more of it. This excess insulin raises levels of a growth signal called insulin-like growth factor 1 (IGF-1), which directly stimulates skin cells and connective tissue cells to multiply faster than normal. The result is epidermal overgrowth, essentially the raw material for a skin tag.
This connection is strong enough that some dermatologists consider multiple skin tags a visible marker worth screening for type 2 diabetes or prediabetes. If you’ve noticed a sudden increase in skin tags, particularly alongside other signs like darkened skin patches in body folds (a related condition driven by the same insulin mechanism), it may be worth having your blood sugar checked.
Body Weight and Skin Tags
Higher body weight increases your risk through two pathways at once. More body fat creates deeper, more pronounced skin folds, which means more friction. But excess weight also tends to worsen insulin resistance, compounding the metabolic trigger described above.
A study of 88 dermatology patients 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. People with obesity had a 2.8-fold higher likelihood. The same study found a statistically significant relationship between abnormal cholesterol and triglyceride levels and skin tag quantity, though the triglyceride link faded after accounting for other metabolic factors. In other words, it’s the broader metabolic picture, not any single lab value, that matters most.
Hormonal Changes
Hormones play a clear role, which is why skin tags often appear or multiply during specific life stages. High levels of estrogen and progesterone during pregnancy are a well-documented trigger. Growth hormone excess, as seen in the rare condition acromegaly, also promotes skin tag formation. These hormones appear to act as growth accelerators for the same skin and connective tissue cells that IGF-1 targets.
Many pregnant women notice new skin tags in the armpits, neck, and under the breasts during the second and third trimesters. Some of these resolve after delivery as hormone levels normalize, though others persist.
Genetics and Family History
The tendency to develop skin tags runs in families. If your parents or grandparents dealt with them, you’re more likely to as well. This genetic predisposition likely influences how your skin responds to friction, how sensitive your tissue is to growth signals like IGF-1, or both. It also helps explain why two people with similar body types and metabolic profiles can have very different experiences with skin tags.
What Skin Tags Are Not
Skin tags are sometimes confused with other growths, but they have a distinct appearance: soft, flesh-colored or slightly pigmented, and attached to the skin by a thin stalk (peduncle). A few key differences can help you tell them apart from similar-looking bumps:
- Warts are caused by a virus (HPV) and tend to have a rough, textured surface. Skin tags are smooth and soft to the touch.
- Seborrheic keratoses look waxy or greasy and appear “stuck on” to the skin surface, often with a rough, scaly texture. They’re usually brown or black.
- Moles are flat or raised with uniform pigment and a symmetrical border, and they sit flush against the skin rather than dangling from a stalk.
- Dermatofibromas are firm, reddish-brown nodules that dimple inward when you squeeze the skin around them. They’re most common on the limbs rather than body folds.
In rare cases, growths that look like skin tags have turned out to be basal or squamous cell carcinomas on biopsy. Any growth that changes color, bleeds, grows rapidly, or looks unusual compared to your other skin tags is worth having a dermatologist examine.
Can You Prevent Them?
There are no proven methods to prevent skin tags entirely. Harvard Health Publishing notes the cause isn’t fully understood and no preventive intervention has been validated. That said, the risk factors point toward practical steps that may reduce how many you develop. Keeping skin folds dry and reducing friction with moisture-wicking fabrics or anti-chafing products addresses the mechanical trigger. Managing blood sugar, maintaining a healthy weight, and staying physically active address the metabolic side. None of these are guarantees, but they target the conditions most strongly linked to skin tag formation.
Existing skin tags don’t need to be removed unless they bother you. They can catch on clothing or jewelry, become irritated, or simply be a cosmetic concern. Removal is straightforward and typically involves freezing, snipping, or cauterizing in a single office visit. Removed skin tags don’t grow back in the same spot, but new ones can form nearby if the underlying causes remain.