You probably don't spend much time staring at your navel. Most of us don't. But if you've ever wondered what is an innie and why some people have a tiny canyon while others have a little knot, you're looking at a fascinating mix of biology and pure, random luck.
It’s just a scar.
Seriously. Your belly button is essentially the very first scar you ever received. It marks the spot where your umbilical cord once connected you to your mother, providing the oxygen and nutrients you needed to grow from a cluster of cells into a human being. Once you were born and that cord was clamped and cut, the stump eventually shriveled up and fell off. What’s left behind is the navel.
Contrary to that old playground myth, your doctor didn't "tie" your belly button into a specific shape. Surgeons and midwives don't use fancy knots to determine your aesthetic. Whether you end up with an innie or an outie is mostly about how the scar tissue heals and how much space exists between your skin and the underlying abdominal wall.
The Anatomy of a Navel
To understand the "innie," we have to look at what's happening under the hood. When the umbilical cord falls off—usually about one to three weeks after birth—the remaining tissue creates a depression. In most people, about 90% of the population, this heals as a hollow. That’s your classic innie.
The "in-ness" of it is dictated by the umbilical ring. This is a small opening in your abdominal muscles. Think of it like a drawstring bag that’s been pulled tight. If the skin attaches deeply to the fascia (the connective tissue) underneath, you get a deep innie. If there’s a bit more scar tissue pushing outward, it might look shallower.
Why do some people have outies?
Sometimes, the healing process is a bit different. An outie isn't "wrong," it’s just a different way the body closes that gap. Occasionally, an outie is caused by a small umbilical hernia. This happens when a tiny bit of intestine or fatty tissue pokes through the muscle layer before it fully closes up after birth. Most of these close on their own by age five, but sometimes the skin remains protruded.
Another cause is a granuloma. This is a small, red piece of "extra" scar tissue that forms while the cord is healing. It’s harmless but can result in a belly button that stands out rather than tucking in.
Culture, Myths, and Belly Button Lint
It’s weird how much weight we put on this. Honestly, there are entire subcultures online debating the "perfect" belly button shape. Surgeons even have a name for the procedure to change it: umbilicoplasty. People actually pay thousands of dollars to turn an outie into an innie because the innie is seen as the "standard" or more "athletic" look in fitness modeling and media.
But let's talk about the practical side of having an innie.
The depth of the navel creates a literal pocket. It collects things. Lint, sweat, dead skin cells, and even bacteria love it there. A study by North Carolina State University, famously known as the "Belly Button Biodiversity Project," found that the average human navel is home to roughly 67 different species of bacteria. Some people had "extremophile" bacteria that are usually only found in soil or deep-sea vents.
Basically, your innie is a tiny, private ecosystem.
The Mystery of Lint
Why is navel lint usually blue? Karl Kruszelnicki, a scientist from Australia, actually won an Ig Nobel Prize for researching this. It turns out that the hair around your belly button acts like a one-way conveyor belt. The scales on the hair trap fibers from your shirt—which are often blue or grey because of denim and common t-shirt dyes—and funnel them directly into the center of the innie.
If you've got a hairy stomach, you're much more likely to find a "treasure" in there at the end of the day.
Changes Over Time: When an Innie Becomes an Outie
Your belly button isn't necessarily a permanent fixture. It can change.
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Pregnancy is the most common reason an innie decides to make an exit. As the uterus expands, it pushes the abdominal wall forward. The tension can cause the navel to flatten out or "pop" into an outie. It’s a bit like a turkey timer. Most of the time, it reverts back to an innie after delivery, but sometimes the skin stays a little stretched out.
Significant weight gain or loss can also change the landscape. Increased intra-abdominal pressure—whether from fluid (ascites) or weight—can force an innie outward. If you notice your innie suddenly becoming an outie and it's accompanied by pain or a bulge you can't push back in, you might be looking at an adult umbilical hernia.
Health and Hygiene for the Deep Innie
Because an innie is a dark, moist, enclosed space, it requires a bit of maintenance. You've probably smelled it at some point—that weird, slightly "cheesy" odor. That’s usually caused by a buildup of Corynebacterium or yeast.
If you don't clean it, you can actually develop an omphalolith. These are essentially "belly button stones." Over years, sebum (skin oil) and keratin (dead skin) mix together, harden, and turn black through oxidation. They can get quite large and even cause infections or ulcers.
- Cleaning is simple: Just use a bit of soap and water in the shower.
- Dry it well: This is the part people miss. Use the corner of a towel to make sure no moisture is trapped.
- Avoid oils: Unless you have very dry skin, putting lotions or oils inside an innie just creates a sticky trap for more bacteria.
Navel Piercings and Scarring
If you're thinking about piercing your innie, the shape matters. A "true" innie has a solid "lip" or "shelf" of skin at the top. This is what the jewelry hangs from. If the navel is too shallow or if the person has a "pseudo-outie," the piercing is more likely to migrate or be rejected by the body.
Healing a navel piercing takes forever. We're talking six months to a year. Why? Because the belly button is a high-movement area. Every time you sit, stand, or twist, you're irritating that scar tissue.
The Psychological Impact of the "Innie"
It’s just skin, right?
Yet, humans are obsessed with symmetry. In a study published in the journal Plastic and Reconstructive Surgery, researchers found that people overwhelmingly prefer a small, T-shaped or vertically oval innie. Horizontal or "hooded" innies were rated lower in terms of attractiveness.
This seems silly, but it drives a massive industry. From body contouring after weight loss to "mommy makeovers," the goal is often to recreate that specific innie look. It represents youth and physical fitness to many, even if that's biologically reductive.
What You Should Watch Out For
While most innies are just "there," certain symptoms warrant a call to the doctor.
- Discharge: If you see clear, yellow, or bloody fluid leaking out, that's a red flag. It could be a simple infection, or in rare cases, a remnant of the urachus (the tube that connected the bladder to the umbilical cord in the womb) that didn't close properly.
- Redness and Swelling: This usually points to omphalitis (infection of the navel). It can happen to adults, not just newborns.
- The "Bulge": If your innie suddenly feels like it has a hard lump behind it, especially one that hurts when you cough or lift something heavy, get checked for a hernia.
Final Practical Steps
If you’ve spent your life ignoring your belly button, maybe give it a quick check tonight.
First, take a peek and see if there’s any redness or "debris" (the aforementioned lint and skin cells). Use a Q-tip dipped in warm water or a very mild soap to gently clear it out. Don't dig too hard; the skin inside an innie is sensitive and thin.
Second, make sure you're drying the area thoroughly after every shower. Moisture is the enemy here. If you struggle with persistent odors despite cleaning, a tiny dab of antifungal cream (like the stuff used for athlete's foot) can sometimes clear up minor yeast overgrowth, but checking with a dermatologist is always the smarter play.
Understand that your innie is unique. Whether it’s deep, shallow, wide, or narrow, it’s just a reminder of your very first connection to life. It doesn't define your health or your fitness—it's just a cool bit of biological history sitting right in the middle of your torso.