Innie vs Outie Belly Button: Causes, Shapes, Hygiene, and When to See a Doctor

Be honest: You're probably looking at your belly button right now, aren't you? Whether it's an innie tucked neatly away or an outie that proudly protrudes, your belly button is a unique mark that tells the story of your earliest connection to life.

“Every single one of us has a belly button because that’s where our umbilical cord was attached before we were born,” explains Min Jing Kong, a trained environmental biologist and Gen Z science content creator for "@justkeepthinikingsg" on Instagram. Your belly button is essentially your first scar, the mark of where your body once connected to your mother before birth.

After birth, doctors cut the umbilical cord, and “the little stump that’s left eventually falls off.” According to Kong, this healing process decides whether you end up with an innie or an outie. The way the tissue closes and scars creates your lifelong belly button type.

According to MedicineNet, approximately 90% of people have an innie belly button, while about 10% have an outie, depending on how the scar tissue forms. ³

Many people believe that how a doctor cuts or clamps the umbilical cord determines whether you'll have an innie or an outie. This is false. The shape of your belly button has nothing to do with the medical technique used during birth. It's entirely about how your individual body heals and forms scar tissue after the umbilical stump falls off.

“About 80 to 90% of people end up with an innie where the scar tissue pulls inwards,” says Kong. This is the most common type, a small depression where the umbilical stump healed inward. “A smaller group of people actually develop an outtie where the scar skips out a little.”

Medical experts confirm that this difference has nothing to do with how the cord was cut, your weight, or your body shape. While the primary factor is how the scar tissue forms during healing, some research suggests genetic factors may potentially play a minor role in the overall shape, though this connection is not definitively proven.

Most people, around 8 to 9 out of 10, have innies, while only about 10 to 20% have outies. ⁴

Kong points out that “it’s not genetic and it doesn’t have anything to do with your weight or body shape.” The reason lies entirely in how the skin and underlying tissue heal after the umbilical cord falls off.

In a few cases, an outie may result from a mild umbilical hernia, when a small portion of tissue bulges through the abdominal wall. This is harmless in most infants and usually resolves on its own as the abdominal muscles strengthen and close the gap naturally. Occasionally, excess healing tissue, called an umbilical granuloma, can also create a small outward bump. These granulomas are small, moist, red lumps of tissue that form in about 1 out of 500 newborns when the umbilical stump area doesn't heal completely. They can be easily treated with simple methods like silver nitrate application, salt treatments, or in some cases, minor surgical removal. ⁵

In some adults, however, a new outie belly button may indicate increased abdominal pressure or an umbilical hernia in adults, especially following pregnancy or rapid weight changes. During pregnancy, belly buttons often change shape, typically around 26 weeks, when the expanding uterus pushes against the abdominal wall. Most belly buttons return to their normal appearance within a few months after giving birth. ^{1, 6}

Doctors advise consulting a healthcare professional if you notice sudden changes in your belly button shape, pain, discharge, or a visible bulge. These could indicate an infection or an umbilical hernia that may require treatment. ¹

An umbilical hernia occurs when tissue such as part of the small intestine or fat pushes through a weak spot near the belly button, creating a visible bulge. In babies and young children, these hernias usually heal on their own by the age of five. However, in adults, they are more likely to cause discomfort or complications and often require surgical treatment to prevent further issues. ¹

“Beyond innie and outtie, belly buttons also come in different shapes, vertical, T-shaped, light bulb, and even swirl,” Kong shares. Each person’s navel has unique characteristics depending on how their skin and muscles formed during healing.

"Beyond innie and outtie, belly buttons also come in different shapes, vertical, T-shaped, light bulb, and even swirl," Kong shares. Each person's navel has unique characteristics depending on how their skin and muscles formed during healing.

Vertical belly buttons look like a narrow oval or slit running up and down, resembling a lowercase "i." This is the most common belly button shape and is often considered aesthetically pleasing.

T-shaped or horizontal belly buttons have most of the fold going horizontally with a depression at the top that makes it appear like the letter "T." The top portion of skin almost completely covers the innermost part of the belly button.

Light bulb-shaped belly buttons have very little hooding at the top and a slightly oval shape that narrows as it goes down, much like an upside-down light bulb.

Swirl-shaped belly buttons are relatively rare and feature folds of skin that create a twisted or spiral appearance around the central opening. 7

Doctors note that a belly button doesn't serve any biological function after birth, it's simply a reminder of your earliest connection to life. Interestingly, all placental mammals, from cats to humans, have belly buttons, though they may look very different across species. Marsupials like kangaroos and egg-laying mammals like platypuses and echidnas don't have belly buttons because they don't develop through a placental connection with an umbilical cord. ⁸

As Kong puts it, “Your belly button is basically your very first scar.” Whether it’s an innie or an outie, it’s simply the result of how your body healed as a baby. It doesn’t reflect your health, your genes, or your weight.

1. Belly Button Biodiversity: Your belly button hosts a remarkable ecosystem. Research from the Belly Button Biodiversity Project found over 2,000 different species of bacteria living in human navels. While this might sound alarming, most of these bacteria are harmless and actually help protect your skin as part of your body's first line of immune defense. ⁹

2. Belly Button Lint: Ever wonder where that mysterious fluff comes from? Belly button lint is a combination of clothing fibers, dead skin cells, and body hair. Research shows that abdominal hair acts like a one-way ratchet, collecting fibers from your shirt and directing them toward your navel throughout the day. Men with hairy bellies tend to accumulate more lint than others. ¹⁰

3. Omphalophobia: Some people have an intense fear of belly buttons, called omphalophobia. This specific phobia can cause anxiety, panic attacks, and avoidance behaviors when seeing or touching belly buttons, whether their own or others'. Even celebrities like Khloe Kardashian have publicly shared their struggles with this uncommon but very real fear. Treatment typically involves cognitive behavioral therapy and gradual exposure techniques. ¹¹

While often overlooked, cleaning your belly button should be part of your regular hygiene routine. Innies, in particular, tend to harbor more bacteria because they create a warm, moist, dark environment where skin folds on itself. This makes them more prone to accumulating sweat, dead skin cells, and debris.

How to clean your belly button properly:

For Innies:

• Use a cotton swab or soft washcloth dampened with warm water and mild soap

• Gently clean around and just inside the belly button

• Rinse thoroughly with clean water

• Dry completely with a clean towel or cotton swab

• Avoid applying lotions or creams inside your belly button, as moisture can promote bacterial growth

For Outies:

• Simply wash with mild soap during your regular shower

• Gently scrub with a washcloth

• Rinse and dry thoroughly

Cleaning your belly button once a week can prevent unpleasant odors, yeast infections, and the buildup of debris. If you notice redness, discharge, persistent odor, or pain, consult a healthcare provider as these may be signs of infection. ¹²

For those unhappy with their belly button's appearance, umbilicoplasty (belly button surgery) is a cosmetic procedure that can reshape the navel. Originally developed to treat umbilical hernias in infants, this procedure has become popular among adults seeking to change their belly button's size, shape, or position.

Common reasons people seek umbilicoplasty include:

• Changing an outie to an innie

• Correcting changes from pregnancy

• Removing scarring from old piercings

• Achieving a more aesthetically pleasing appearance

The procedure is typically quick (about one hour) and can be performed under local anesthesia. Recovery is relatively fast, with most people returning to work within a few days. Umbilicoplasty can be done as a standalone procedure or combined with other body contouring surgeries like a tummy tuck. ¹³

After birth, a small segment of the umbilical cord, approximately 2–3 cm, remains attached to your baby’s navel as the cord stump. Over the next 7 to 14 days, this stump darkens, dries out, shrivels, and then naturally detaches.

Once it falls off, a small wound remains and gradually heals into the baby’s belly button. It’s important to keep the area clean and dry: wash hands before handling the stump, avoid using creams or antiseptics, and let the nappy sit below the stump so it can air dry. ²

References:

1. Cleveland Clinic. “Umbilical Hernia.” Cleveland Clinic, last reviewed June 13, 2023. https://my.clevelandclinic.org/health/diseases/umbilical-hernia.

2. Children’s Health Queensland – Hospital and Health Service. “Caring for Your Baby’s Umbilical Cord Stump and Belly Button.” Reviewed May 2023. Last updated December 2023. Accessed October 19, 2025. https://www.childrens.health.qld.gov.au/health-a-to-z/caring-for-your-babys-umbilical-cord-stump-and-belly-button.

3. MedicineNet. “What Is the Belly Button For?” MedicineNet, updated 2024. https://www.medicinenet.com/what_is_the_belly_button_for/article.htm

4. Verywell Health. “Outie Belly Button: Causes and When to See a Doctor.” Verywell Health, updated 2024. https://www.verywellhealth.com/outie-belly-button-7479658

5. WebMD. "Umbilical Granulomas: Causes, Treatments, and Prevention." WebMD, June 24, 2025. https://www.webmd.com/parenting/baby/what-to-know-about-umbilical-granulomas

6. Cleveland Clinic. "Belly Button Changes During Pregnancy."

7. Healthline. "Belly Button Types, Shapes, and Sizes." Healthline, April 7, 2020. https://www.healthline.com/health/belly-button-types

8. Independent. "World's Most Bizarre Mammals: Monotremes." The Santa Barbara Independent, November 7, 2009. https://www.independent.com/2009/11/06/worlds-most-bizarre-mammals-monotremes/

9. Hulcr, Jiri, et al. "A Jungle in There: Bacteria in Belly Buttons are Highly Diverse, but Predictable." PLOS ONE, November 7, 2012. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0047712

10. Steinhauser, Georg. "The Nature of Navel Fluff." Medical Hypotheses 72, no. 6 (2009): 623-625. https://www.sciencedirect.com/science/article/abs/pii/S0306987709000474

11. Healthline. "Omphalophobia (Fear of Belly Buttons): Symptoms and Treatment." Healthline, January 10, 2020. https://www.healthline.com/health/omphalophobia

12. Cleveland Clinic. "How To Clean Your Dirty Belly Button." Cleveland Clinic Health Essentials, April 28, 2025. https://health.clevelandclinic.org/how-to-clean-belly-button

13. Healthline. "Umbilicoplasty: Purpose, Procedure, Recovery, and Risk." Healthline, April 2, 2018. https://www.healthline.com/health/umbilicoplasty

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