That horizontal line or crease beneath your chin is almost always the result of how skin, fat, muscle, and bone interact in the submental region, the area between the underside of your chin and the front of your neck. For most people it is not a sign of anything medically worrying. The line forms where skin folds against itself due to some combination of natural anatomy, fat distribution, skin elasticity, posture habits, or age-related changes in the tissue layers beneath the surface. Understanding which of those factors is driving yours helps explain whether it is likely to change over time and what, if anything, can be done about it.
What Is Actually Happening Beneath the Skin
The submental area has a surprisingly complex architecture. Directly under the skin sits a defined fat compartment, bounded by fibrous walls called septa. Cadaveric studies have mapped this compartment in detail, identifying a front boundary (the “submental septum”), a rear boundary (the “suprahyoid septum” near the hyoid bone), and side boundaries formed by the digastric muscles.1PubMed Central. The submental fat compartment of the neck These septa are bands of connective tissue that tether the skin to deeper structures. When fat accumulates in this compartment, or when skin loses elasticity and starts to drape, the tethering points created by these septa can produce visible creases on the surface. The same basic mechanism explains cellulite elsewhere on the body: fibrous bands pulling the skin inward while softer tissue herniates between them.2PubMed Central. A Study of a Novel Controlled Focal Septa Release Method for Improving Cellulite
Beneath the fat sits the platysma, a thin sheet of muscle that stretches from the collarbone up to the jawline. Unlike most facial muscles, the platysma has very little bony attachment. Over time it loosens its grip on the mandible, thins out, and can develop a resting tone that pulls downward on the lower face. This loosening contributes to jowling and a less defined jawline, and the horizontal creasing that accompanies these changes often shows up as a visible line under the chin.3PubMed Central. Platysma Prominence: Review and Expert Analysis of Clinical Presentation, Burden, and Treatment Considerations When the platysma contracts, it can also deepen any existing crease by bunching the overlying skin.
How Your Bone Structure Sets the Stage
Not everyone who has a submental line is dealing with excess fat or aging skin. The shape and position of your jawbone and hyoid bone play a major role in how the under-chin area looks, even in young and lean individuals. In what researchers call a “balanced” neck profile, the hyoid bone sits at or above the level of the lowest point of the chin.4PubMed. Problem neck, hyoid bone, and submental myotomy When the hyoid sits lower than that, or when the mandible itself is small or set back (a trait sometimes called a receding chin), the angle between the chin and neck becomes more obtuse. A blunter chin-neck angle gives the skin fewer sharp bony landmarks to drape over, so it folds more easily and a horizontal crease becomes more prominent.
This is largely genetic. The hyoid bone’s position tracks closely with where the mandible sits. When the jaw is surgically advanced, the hyoid tends to follow it forward, which tightens the under-chin profile.5PubMed. Hyoid bone position after surgical mandibular advancement That relationship explains why some people with strong, forward-projecting jawlines rarely develop a visible submental crease even with weight gain, while others with smaller or more retruded chins notice one even at a healthy weight.
The Role of Body Fat
Weight gain is the factor most people suspect first, and it is often part of the picture. The submental fat compartment sits in a spot that is prone to early and stubborn fat deposition, and for many people it is one of the last places to slim down during weight loss. Even a modest increase in fat in this compartment can push the skin outward enough to create a fold where the chin meets the neck, producing that characteristic horizontal line. This is sometimes what people mean colloquially by a “double chin.”
But body weight is only one variable. Because the compartment is bounded by septa that anchor the skin at fixed points, the line can persist even after significant fat loss. The septa do not stretch or remodel the way fat does. Once they have been pulling the skin into a crease for months or years, the crease can become essentially permanent, reinforced by changes in the skin itself. This is why some people who lose a great deal of weight find that their submental line does not fully resolve.
Aging, Collagen, and Skin Laxity
If you first noticed the line in your thirties or later, skin aging is a likely contributor. The dermis gradually loses both collagen and elastin fibers over time, which reduces its ability to snap back into place after being folded or compressed.6PubMed Central. Collagen Supplements for Aging and Wrinkles: A Paradigm Shift in the Fields of Dermatology and Cosmetics Skin also becomes thinner as dermal thickness decreases. On the face and neck, where skin is already relatively thin compared to the trunk, these changes show up earlier and more visibly. A crease that was barely noticeable at twenty-five can deepen noticeably by forty, not because anything new is happening underneath but because the skin is less forgiving of the folds that were always there.
Sun exposure accelerates this process in the neck and chin area, which many people neglect when applying sunscreen. The cumulative effect of UV damage on collagen is well established, and the submental skin, which often faces slightly upward, can catch reflected light from surfaces below even when the rest of the face is shaded.
Posture and Repetitive Motion
A significant modern contributor that did not exist a generation ago is the amount of time people spend looking down at screens. When you tilt your head forward, the skin under the chin compresses into a fold. Do this for a few minutes and the skin bounces back. Do it for several hours a day, every day, for years, and the crease can become etched into the skin in the same way that sleep lines on the side of the face can become permanent. Dermatologists have started using the informal term “tech neck” to describe the horizontal lines that appear on the front of the neck and under the chin from habitual downward head posture.
Interestingly, while sleep position might seem like a similar repetitive force, the research does not strongly support the idea that sleeping on one side causes asymmetric facial aging. A study comparing right-sided and left-sided sleepers found no significant link between sleep side and the amount of wrinkles or facial sagging on that side.7PubMed Central. Effect of sleep position on perceived facial aging So while sleeping face-down might theoretically compress the chin area, the evidence for sleep position as a major driver of facial lines is weak. Waking posture, particularly the hours spent hunched over a phone or laptop, is a far more plausible culprit.
When the Line Appears on Younger, Leaner People
If you are in your teens or twenties, at a normal weight, and still see a distinct line under your chin, the explanation is almost certainly structural rather than age-related. A shorter or more recessive mandible, a low hyoid position, or simply the way your particular submental fat pad is shaped can create a visible crease regardless of overall body composition. Some people also have a naturally thicker submental fat pad relative to the rest of their face, which is a genetic trait unrelated to being overweight.
Skin thickness varies across the face. Ultrasound measurements show that chin skin is among the thicker facial sites in most people, but there is meaningful variation by individual, sex, and body mass index.8PubMed Central. Ultrasonographic analysis of facial skin thickness in relation to age, site, sex, and body mass index Thicker skin in the chin area may resist creasing more than thinner skin, which could partly explain why the line is prominent on some young people and invisible on others with similar jaw structure. The point is that having a line under your chin at a young age is not unusual and is not necessarily a sign that anything is going wrong. It is a normal anatomical variant for many people.
Can You Get Rid of It Without Surgery?
The approach depends entirely on what is causing your particular crease. If excess submental fat is the main issue, injectable deoxycholic acid (marketed as Kybella in the United States) is a non-surgical option. The drug destroys fat cells on contact when injected into the submental compartment. Clinical trials have shown that the fat reduction lasts: improvements measured twelve weeks after the final treatment session were largely maintained at extended follow-up periods of two years or more, generally without worsening skin laxity.9PubMed. Deoxycholic Acid: A Review in Submental Fat Contouring The treatment typically requires multiple sessions, and swelling afterward can be substantial, but the fat cells, once destroyed, do not regenerate.
If the line is more about lost volume or a weak chin projection rather than excess fat, hyaluronic acid fillers injected into the chin and jawline can restore definition. In an eighteen-month study, roughly three-quarters of patients treated with chin filler showed at least a one-grade improvement on a clinical volume scale, and satisfaction rates were high at final follow-up.10PubMed Central. Using injectable fillers for chin and jawline rejuvenation Filler works by giving the skin more structure to drape over, which can reduce the appearance of the submental crease even without directly treating it. The downside is that hyaluronic acid fillers are temporary, typically lasting one to two years before reabsorption.
For skin laxity contributing to the line, radiofrequency and ultrasound skin-tightening devices are sometimes marketed as solutions. Evidence for these is more mixed, and the results tend to be subtle compared to what injectable or surgical treatments can achieve. Topical retinoids and daily sunscreen can slow further collagen loss but will not reverse a crease that has already formed.
Surgical Options for a Defined Jawline
When the crease is deep, the chin-neck angle is obtuse, or multiple factors are at play simultaneously, surgery becomes the most effective option. The most targeted procedure is a submentoplasty, which addresses the under-chin area specifically through a small incision hidden in the natural submental crease. The surgeon can remove excess fat, tighten the platysma muscle, and sometimes modify the deeper strap muscles of the neck to sharpen the angle between chin and throat.11PubMed. Isolated submentoplasty. A limited approach to the aging neck Techniques that plicate (fold and stitch) the platysma and suprahyoid strap muscles together have shown good results for correcting the “double chin” contour.12PubMed Central. Plication of Neck Strap Muscles and Platysma for Double Chin Correction – A Retrospective Study
For patients whose main issue is a receding chin rather than excess soft tissue, a chin implant or sliding genioplasty (where the chin bone itself is cut and repositioned forward) can dramatically change the under-chin profile. Advancing the mandible pulls the hyoid bone and attached soft tissues forward with it, which tightens the submental area from the inside out. This is why orthodontic jaw surgery in patients with significant mandibular retrusion often produces a noticeably cleaner jawline as a side effect, even though the surgery was done for bite correction rather than aesthetics.
Submentoplasty has been described as particularly useful for patients with an obtuse chin-neck angle who are not ready for or do not need a full facelift.13The Journal of The Korean Dental Association. Submentoplasty for esthetic improvement of the neck-lower facial region In reconstructive contexts, surgeons have also used local fat flaps from the submental and labiomental areas to rebuild chin contour in patients who lost tissue from burns or trauma.14PubMed Central. Retrusive chin reconstruction after burn injuries using submental and labiomental fat flaps: an innovative method
Common Misconceptions
The biggest misunderstanding is that a line under the chin equals being overweight. While fat is often a contributor, plenty of lean people have a prominent submental crease because of their skeletal structure. Conversely, some people with significant submental fat do not develop a visible crease because their jaw projects far enough forward to keep the skin taut. Assuming the line is purely a weight issue can lead people to pursue aggressive dieting that will not resolve an anatomical crease.
Another misconception is that chin exercises or jaw-clenching devices can eliminate the line. The platysma and the muscles of the floor of the mouth can be exercised, but strengthening them does not address the fat compartment, the septal tethering, or the skin laxity that typically cause the crease. At best, jaw exercises might mildly firm the area; at worst, aggressive platysma engagement can actually accentuate vertical neck bands over time as the muscle hypertrophies unevenly.
Finally, people sometimes confuse a submental crease with a “witch’s chin” or mentalis strain pattern, where the chin pad puckers and the labiomental crease deepens due to overactivity of the mentalis muscle. That is a different issue, usually treated with small doses of botulinum toxin to relax the muscle. If the line you are noticing is actually on the chin pad itself rather than beneath it where the chin meets the neck, mentalis dysfunction might be what you are seeing.
Why Humans Have Such Prominent Chins in the First Place
It is worth noting that the prominent chin is a uniquely human feature. No other living primate has one. For decades, researchers debated whether the chin evolved for a specific purpose, such as resisting the mechanical stresses of chewing or speech. A recent evolutionary analysis compared human and ape craniofacial form and concluded that the chin likely evolved largely as a by-product of other changes: the reduction in front tooth size, increased flexion of the skull base, expansion of the braincase, and the flattening of the lower face that came with bipedalism. Of nine chin-specific traits analyzed, only three showed evidence of direct evolutionary selection; the rest appeared to have come along for the ride.15PubMed Central. Is the human chin a spandrel? Insights from an evolutionary analysis of ape craniomandibular form
This matters for the submental crease question because it means human chin anatomy is, in a sense, an evolutionary accident. The bony shelf that creates the chin-neck angle, and that determines how sharply or gently the skin transitions from face to neck, was never specifically “designed” by natural selection for any particular profile. Variation in chin prominence across the human population is enormous, and none of it represents a defect. The line under your chin is a product of the particular geometry your face inherited, shaped by forces that had nothing to do with appearance.