What Is A Uniboob?

 tattooed woman in glasses with short dark hair holding the side of a black racerback bralette

I’m well acquainted with the uniboob. I haven’t worn an underwire bra in about 5 years, so I am almost always in a sports bra or triangle bralette. Combined with my need for a bralette for large bust, I’m a frequent victim of the uniboob. Instead of two separate boobs, I look down to discover my two girls have morphed into one lump of boob sitting in the center of my chest.

While the look isn’t my favorite, it’s also really uncomfortable! Boob sweat, rashes, and pain occur all because my boobs decide they want to hold hands all day. If you’ve suffered from uniboob and are looking for a solution, keep reading! I’ll go over what a uniboob is, what causes it, and how to prevent one.


Uniboob is a condition where two boobs are pushed together by a bra, making it appear like there’s just one giant boob. It's most common for people with larger breasts, but anyone can fall victim to it. Sports bras and other compression bras are the most frequent offenders.

Uniboob, which is a temporary condition caused by a bra, is different from Symmastia, a medical condition we’ll break down a bit more below.

a backlit thin woman wearing a black bra is straddling and about to kiss a thin man in side profile


For many people, a uniboob is more than just a look they’re trying to avoid. It causes some serious discomfort from issues like:


Boob sweat is a reality everyone with boobs has to deal with at some point. More well endowed folks tend to suffer from worse boob sweat, but exercise, humidity, or an ill-fitting bra can all contribute to that feeling of sweat dripping between your breasts.

With a uniboob, your boobs are pushed together leaving very little space in between the two. This makes boob sweat 1000% worse, in my personal opinion. The two boobs touching create sweat of their own, plus the sweat that normally drips between your boobs gets stuck in your cleavage. Long story short, it’s an uncomfortable mess.


I think the word "rash” is on par with “moist” for words I hate the most. Even worse than the word is the reality of having a rash on your boobs. Yeast infections and other rashes can be caused by hot and wet conditions, which uniboob causes.

It’s itchy, painful, and usually requires a trip to the pharmacy to get some anti-fungal cream to clear it up. I can think of other ways to spend a Friday night rather than smearing anti-fungal cream on my boobs, but that’s just me.


Most uniboobs are caused by ill-fitting bras pushing your boobs together. That stretching of the boobs to meet in the middle can be extremely painful on the outer sides of the breasts.

Instead of supporting from underneath, bras that cause uniboob compress and push them together, so it can also cause upper back pain from the lack of support.

 a thin white woman stretching her hands above her head while wearing a black triangle bralette


While you might be most familiar with thigh chub rub, chafing occurs when any two body parts are rubbing together in a moist environment.

Hello—that’s a perfect description of a uniboob. Your two boobs are sweaty and rubbing up against each other. You feel burning all day only to reveal a red rash between your tatas after you finally release them from your bra—not fun!


I know I said that the issues with a uniboob goes beyond just aesthetics. However, if having a uniboob makes you feel less confident in yourself, I’m not here to discount your feelings. This plus all of the above issues mean it’s worth it to prevent a uniboob before one even starts to form.


Close up of a torso on a person wearing a matching green racerback bra and boxer set

Now that we’ve answered the all-important question—what’s a uniboob, it’s time to figure out what causes one. There are many different reasons your boobs can look like they’ve morphed into one, but these are the most likely:


Sports bras are probably the most common cause of a uniboob. Many of them don’t offer separate cups for each boob. This means one piece of fabric covers both, resulting in your boobs being pushed together.

They’re also typically made to be fitted tightly to protect your tatas while engaging in low or high impact exercise. This tight fit squishes your boobs to your chest and together–creating a very flat uniboob look.

All of the worst issues associated with a uniboob, like boob sweat and chafing, are especially present when exercising in a sports bra because of the increased body heat and movement.


Bras with heavy compression either for post-surgery healing or to minimize the size of breasts are infamous for the uniboob phenomenon. Just like high impact sports bras, the compression on these bras push your boobs into your chest forming one long uniboob.

If you’re experiencing uniboob with a post-op compression bra, it’s more important to be comfortable and all healed up before worrying about the temporary look of your boobs. Boob sweat, chafing, and rashes are all serious concerns to the healing process though. You can always sprinkle tapioca powder in your bra to absorb your sweat.

With gender-affirming minimizing bras, the aesthetics are a crucial part of wearing one. However, if you’re experiencing pain, chafing, or rashes, it’s important to find ways to prevent those issues. We’ll go over some below.

a thin, heavily tattooed, adrongynous person with long black hair wearing a green bra


Camisoles are another repeat offender when it comes to the uniboob, thanks to the built-in shelf bra. A shelf bra is simply a piece of fabric that covers both boobs with a strip of elastic underneath to hold it in place.

Much like sports bras, when a single piece of fabric covers both boobs, you’re more likely to experience uniboob as it will push them together.


When sports bras or other full coverage bras fit too tightly, that extra compression can cause uniboob even with built in cups. Because the boobs are so tightly pressed against the chest, they expand flatly into a uniboob.

Cupped bras that are too loose can also cause uniboob if the boobs are naturally less full. A loose bra will not lift up and support them, so the boobs will droop down while being pushed together by the outer sides of the cup.


plus size woman with big boobs wearing a black racerback bra showing what’s a uniboob

Did anybody else want to sell their soul for a pair of huge boobs during puberty only to discover that it’s not all it’s cracked up to be? No, just me? Perfect.

For most people with big boobs, uniboob is an inescapable reality with sports bras and clothing fitted to the breast. Even when my bra isn’t causing uniboob, a tightly fitted top can squish my boobs together into one with some pretty out-of-control cleavage.

If you have big boobs and experience uniboob frequently, finding ways to minimize the side effects is essential.


Synthetic materials like polyester and rayon are infamous creators of what I like to call swamp boob. Sweaty, itchy, and hot, it’s not a pleasant experience in the least. Combine that with a uniboob? You’re in for a rough time, my friend.

Some of the most common issues associated with uniboob like chafing, boob sweat, and rashes are all made worse by a moist (there’s that word again) environment. If your bra is made of synthetic materials, your uniboob is going to be much, much worse than a regular one.


Symmastia is different from uniboob because it’s a real medical condition. Instead of simply appearing to have two boobs morphed into one, people with symmastia’s breasts have grown together, leaving very little or no cleavage between them.

Some people are born with congenital symmastia, but it’s more common to have acquired symmastia from breast augmentation or reconstruction surgeries. The implants can move together from their individual tissue pockets, usually due to surgeon error.

Both types are incredibly rare and can be treated with surgery. However, because it doesn’t cause any serious health problems, it’s a cosmetic fix. Some people decide they’d rather rock the one boob look than go through a surgery–understandable!


We’ve gone over what is uniboob, the problems one can cause, and what causes them. Now, we’ll talk about preventing one so you can avoid the one mega-boob experience and live more comfortably in your bras.


a black triangle bralette with defined cups laid flat on a white comforter with a rose on either side

The best, almost sure-fire way to avoid a uniboob is to wear bras with defined cups. This way your boobs have a defined area to exist in, separate from the other.

Many of the worst offenders of uniboob are bras with one piece of fabric covering both boobs, so having separate pieces helps support, lift, and separate each one.

Just because I’m recommending a more typical bra style does not mean I’m recommending an underwire bra. Bras like the triangle bralette keep your tatas separate, while supporting each one with soft hemp and no underwire to be found.


As bras go through normal wear and tear of being the primary support of your boobs, they become looser. Washing especially can degrade your bras if you’re machine washing or using harsh detergents.

When bras become loose, they do not support your boobs as well. This lack of support can cause uniboob because your boobs will just fall towards one another instead of being lifted.

 a bathroom sink filled with black bras being hand washed under the faucet

Learning how to hand wash bras can save you from having to pitch your favorite one after only a year. It’s also better for the environment because it saves water and conserves energy–a win-win!

Bras also tend to become looser with wear. If you’re experiencing uniboob even with your cupped bras, check when you last purchased a new one.


Each person's body is different depending on the day and hour, even depending on their last meal. So if you’re not adjusting your bra each time you put it on, that might just be the cause of your uniboob.

There’s two parts of the bra to adjust when experiencing a uniboob: the straps and the clasp.

Knowing how to tighten bra straps can lift your boobs upwards and apart. If the straps are too tight, there might be too much compression on your boobs, forming a uniboob. Find your inner Goldielocks and discover your perfect middle ground on strap tightness.

A normal bra clasp has three different sets of hook and eye closures, so you can adjust the band tightness. You should always start your bras on the loosest setting, tightening as the bra becomes older and looser. If you start off with too tight, the extra compression can cause uniboob.

smiling woman in a comfy black racerback bra lounging on her couch in a white, fuzzy cardigan


For me, I don’t really care about the look of the uniboob as much as I do about the discomfort I feel when I have one. A lot of the issues associated with uniboobs like boob sweat, infections, and chafing are caused by moist environments or scratchy materials.

That’s why I love hemp bras. Items from hemp clothing brands are naturally antibacterial, super soft, and moisture wicking. That’s why hemp is the perfect material for bras–it absorbs boob sweat, won’t chafe against your skin, and allows more breathability to prevent infections.


I’m a big fan of pull-over-your-head sports bras, especially a racerback bralette. I like the full coverage, snug feel, and comfy fit. I don’t love it when they make me have a uniboob, though.

To avoid this and still be able to wear my fave bras, I pay special attention to the fit. With a too-tight sports bra, you’ll experience uniboob thanks to all of the extra compression. However, if it's too loose, you lose all support. Finding one that fits you snugly and flexibly keeps your boobs separate but still supported.

a black triangle bralette is laid out next to a black racerback bralette on a wrinkly off-white linen cloth.


Like most clothes, bras can be incredibly important to self-expression. If you’re wearing a gender-affirming bra, having a uniboob can be an unpleasant experience, to say the least.

While some people choose to wear binders to minimize the appearance of breasts, they can be incredibly expensive and inaccessible. Thankfully, there are organizations that provide free chest binders to trans and non-binary folks that cannot access them.

However, if you’re experimenting or have smaller breasts, you might first start with a compression bra to test the waters. Compression bras can cause uniboob for all of the aforementioned reasons.

To avoid the uniboob look with a gender-affirming bra, a tighter fitting bra can do the trick. You can also layer two sports bras on top of each other. Just be sure to take care of yourself and if you have any trouble breathing, give yourself a break. Wearing loose clothing over the compression bra will also minimize the uniboob look.

a thin white woman exposes her green bralette and torso under and open flannel shirt


Uniboobs can be unavoidable when you’re living in a body with breasts, but that doesn't mean you have to suffer the accompanying boob sweat, rashes, or chafing in silence. I think it’s time to shout about uniboobs from the rooftops!

After all, how many people without breasts even know the answer to, “what is a uniboob?” How about we do a little educating? In four emojis or less, how would you describe uniboob?

Underwear Blog | Hemp Blog | WAMA