Bulging skin under your arms? Here is how to pick the right bra

That little bulge under your arm usually isn't extra fat. It's a bra that isn't holding you in at that exact spot. A cup that's too small, a side panel that's too low, or a band that's stretched out: the tissue has to go somewhere, so it pushes over the edge. Switch to a bra with a higher side panel and the right size, and the bulge usually disappears on its own.

Of the nearly 2,900 women we asked about this, 9.6% say the shape of their bra shows through their clothes, often right at this spot. Below are five possible causes, each with a test you can run right now, in the bra you're already wearing. Work through them one by one: it's often not a single cause but a combination that keeps bringing the bulge back, even if you've already tried switching bras.

1. Your cup is too small, so tissue pushes out to the side

A cup that's too small simply doesn't give your breast enough room. The tissue that doesn't fit looks for the only way out: sideways, toward your armpit. That's the bulge you see in the mirror, even when the rest of the bra fits fine.

Try this: stand in front of a mirror in your bra, arms relaxed at your sides. Look sideways: does tissue spill over the edge of the cup toward your armpit? Then the cup is a size too small, even if the band itself doesn't feel tight.

"Beautiful cups, but I still get bulges under my arms"

This customer put it exactly right: the cup itself fits well, but there's just not enough room, so the bulge shows up anyway. The fix isn't a tighter bra. It's more cup volume. If you currently wear a 36C and still see a bulge under your arm, try a 34D instead. Those two sizes hold roughly the same volume, but the cup gives you more room without loosening the band. The Daily Essential Bra goes up to cup H, so you don't have to trade comfort for a bigger cup. If you're stuck between two sizes, go with the bigger cup. Too much room in a cup can still be fixed with a snugger band. Too little room can't.

2. The side of your bra is too low or has no structure

Some bras are really only designed for the front. The cup holds your breast in place, but the side panel stops well before your armpit, or it's made of thin, floppy fabric with no shape at all. There's literally nothing holding the tissue in on that side, so the bulge just hangs there, unsupported.

Try this: put your finger where the cup meets the side panel of your bra. Does that point end partway across your side, well before your armpit? Then that bra simply doesn't have enough fabric to hold the bulge in, no matter how good the size is.

When you shop for a new bra, don't just check the cup. Check how far the side panel extends too. A double layer of fabric that holds the tissue together at the side prevents exactly this: no spilling over, no bulge hanging over the edge. The Daily Essential Bra is built around this, with extra-high side panels that extend past your armpit. Those extra inches of fabric make the difference: they catch the tissue before it gets the chance to hang over the edge, without making the bra feel tighter or less comfortable.

If the side panel feels floppy rather than too low, read more in Floppy side panel under your arm: cause and fix.

3. The band is stretched out, or it was always too loose

Elastic wears out. After dozens of washes, the band loses its stretch, and a band with no stretch left can't hold the tissue at the side in place anymore. If the band was already too loose when you bought it, this problem starts from day one.

Try this: close your bra on the last hook, not the first. Can you still slide two fingers or more under the band at your back? Then the band is too loose and has no grip left, including at the side.

Among the nearly 2,900 women we surveyed, 8.2% name a bra that sags or no longer supports as one of their biggest frustrations, and that often comes down to exactly this. If you're on the last hook and the band is still loose, go down a band size. If a bra that used to fit fine feels softer and looser after a few months, it's simply time for a new one. Rotate between two bras so the elastic gets a chance to recover between wears and stretches out more slowly.

4. Your bra isn't sitting level around your body

A band that rides higher in the back than in front pulls at an angle around your body. That angle doesn't push tissue straight back, it pushes it sideways, right under your arm. This often happens without you noticing, because the bra still looks fine from the front.

Try this: stand sideways in front of a mirror. Does the band sit noticeably higher in back than in front? Then your bra is sitting at an angle, and that's a separate cause of the bulge, apart from your size.

Fix this by tightening the band so it sits level all the way around, or by checking whether your bra has already crept up your back. Read more in Bra creeping up your back or riding up your stomach: how to stop it

5. You're wearing a style with no side support

Bralettes and very thin wireless bras feel soft, but they often have no structure at the side at all. On a smaller frame that doesn't always show, but once there's more tissue to hold, it just hangs loose over the edge. This is a different issue than loose skin from age or weight loss: here the cause is the bra's style, not your skin.

Try this: take off your bra and run a finger along the inside of the side panel. Do you feel only thin fabric, with no firmness or double layer at all? Then this style simply wasn't built to hold a bulge in.

Not sure if it's excess skin rather than your bra, read the difference in Excess skin under your arm after your bra: what can you do? If you wear this style mostly at home or under loose clothing, reach for a bra with a sturdier side panel for the hours you're standing or moving around more.