Underwire bra hurts under the arms: here's what you can do

An underwire that digs in or pinches under your arm almost always comes down to one simple mismatch: the shape of the wire doesn't match the shape of your body right at that spot. Usually the cup is a touch too small, the band is too loose, or the wire itself got bent out of shape after a few years of faithful service. Below, you'll find each cause, a test you can do right now to spot it, and what actually fixes it. Your posture and the way you put the bra on can play a role too, since a crooked fit when you're getting dressed can shift the pressure before your day even starts.

Cause 1: your cup is too small, even if the band feels fine

An underwire is shaped to wrap all the way around your breast tissue, including the part that runs toward your armpit. If your cup is too small, all that tissue doesn't fit inside it. It gets pushed outward, right to where the wire sits. That's the moment it starts to cut in.

The wire cutting into my skin until it hurt right under my arm

This is one of the most common complaints we hear, and it's almost never about the wire itself. It's about the size around it.

Try this: stand sideways in front of a mirror with your bra on. Do you see a bulge of tissue poking out above or beside the wire, toward your armpit? Now try this too: slide two fingers flat between the wire and your armpit. Do you feel tissue pushing back against them right away? Then your cup is too small, even if the band feels okay otherwise. Also check whether tissue spills over the top of the cup. That's just as clear a sign as the bulge on the side.

What to do about it: go up a cup size and usually down a band size, so the total volume works out right. Say you currently wear a 36C and still see that bulge. Try a 34D or 36D instead. Not sure if your cup fits right on the side? Read our article on a bra cup that's too wide on the side, since that's basically the mirror image of this problem.

Cause 2: the band is too loose, so the wire rides up

The band carries most of the weight of your bra, not the straps on your shoulders. If the band is too loose, the whole bra works its way up over the course of the day. And when the bra rides up, the wire goes with it, until it ends up right under your armpit instead of around your breastbone.

Try this: with your bra fastened on the loosest hook, pull on the band at your back. Can you slide more than two fingers under it without any effort? Then the band is too loose. Try this too: raise your arms over your head. Does the whole bra, band included, ride up with them? Then your band size is too big, plain and simple. Also check whether you're already on the loosest hook. If the bra is fastened on the tightest hook and the band is still loose, the band size is too big no matter what.

What to do about it: go down a band size and up a cup size to compensate, so there's still enough room for your breasts. So instead of keeping a 36C and just pulling it tighter, head toward a 34D.

Cause 3: the wire itself is bent or worn out

Metal warps. After a wash on the wrong cycle, a tumble in the dryer, or just a few years of wear, the tip of the wire bends slightly off from where it's supposed to sit. Right at your armpit, where the wire is narrowest and most curved, you'll feel it first.

Try this: take the bra off and lay it flat on a table, cup facing up. Does the wire lie completely smooth against the fabric, in a nice round line? Or does the end near the armpit stick up or out to the side? Run your finger along the whole wire too. Do you feel a kink, a bump, or a sharp point poking through the fabric? Then it's done. Wires that have sat crooked on one side for a while often show it on the outside of the fabric too, as a slight discoloration or a thin worn spot.

What to do about it: replace it. A bent wire doesn't bounce back into shape, and bending it straight yourself only weakens the metal further, so it goes crooked again faster or even pokes through the fabric.

Cause 4: you have fuller sides, and most wires don't account for that

Some women carry more breast tissue toward the side, near the armpit, than others. A standard wire follows one fixed, straight curve. If that curve doesn't follow your side, you get a pinch right at that spot, no matter how well the rest of the size fits.

Try this: put your bra on and use your flat hand to push the tissue on the side of your breast forward, into the cup. Does the tight spot near your armpit disappear when you do that? Then it's not your size, it's the style. The wire simply doesn't follow your shape there. This shows up more often with an asymmetrical bust, where one side is a bit fuller than the other, so the same wire fits on one side and pinches on the other.

What to do about it: look for a style with high sides that wrap around the tissue instead of pushing it away. If you also deal with skin folding over the band, read about bulges hanging under your armpit from your bra, since that's a slightly different problem with a similar fix.

Cause 5: a wire presses there simply because it's there

Sometimes there's nothing wrong with your size, your style or your wire. The problem is the wire itself. It's a piece of stiff plastic or metal, right where your arm moves all day long. Every time you lift your arm, bend it, or reach forward, that stiff edge presses into skin that's already thin and sensitive to begin with. Temperature changes play a role too: in warm weather skin swells up a bit more, so a wire that usually fits fine starts pressing sooner in summer.

Of the nearly 2,900 women we surveyed about their biggest bra frustration, 32.8% named the underwire itself, and 23.3% specifically mentioned poking, pressing or cutting in. That's more than a quarter, and it's a physical complaint, not a cosmetic one. Women describe it in their own words: red marks, wires stabbing under the arms, a wire that hurts and feels miserable.

What to do about it: try a bra without an underwire. That's why our Daily Essential Bra is made completely wire-free. Instead of a stiff wire, it has a 3-inch-wide band that takes the weight off your shoulders and supports from below. The memory foam cups mold to your breast instead of the other way around, and a double layer of shaping on the side holds everything in place so nothing spills out to the side anymore, right where the wire used to poke. It comes in sizes S through 3XL+, with a size chart that goes up to cup H. Want to browse a few wire-free styles first? Check out the full wire-free bra collection.