Can Ultherapy, ONDA or Fat-Dissolving Injections Correct Facial Asymmetry?

한국어 · English · 简体中文 · 繁體中文 · 日本語

By Daebbang

“The right side of my face is bigger. Could you do more Ultherapy or ONDA on that side?”

“If I get more fat-dissolving injections on the bigger side, won’t the two sides look more alike?”

I hear questions like these often in the clinic. When one side looks bigger, it seems reasonable to try to reduce that side more.

But there is something we need to check first. Does the bigger side really have more fat? Or are the muscles or bones underneath different in size or shape?

Here is my answer: when fat or sagging contributes to the difference, an appropriate treatment may improve part of it. But if the main reason is the masseter muscle or the facial skeleton, simply doing more Ultherapy, ONDA or fat-dissolving injections is unlikely to solve it.

Why does one side of the face look bigger?

Skin and fat are not the only things that determine facial shape. The shape and position of the bones, the size of the masseter chewing muscles, the amount and distribution of fat, and sagging of the skin and soft tissues all play a part.

Recent chewing habits or weight changes cannot explain every difference. Studies in growing children have linked facial and jaw asymmetry with childhood head and facial shape, as well as a jaw shift to one side when the teeth come together. Some differences have been present since childhood. [1] [2]

There is research in adults, too. An analysis of CT scans from 221 adults seeking dental care found that differences in the positions of surface features, including the lips and the area beneath the nose, were associated with differences in the underlying skeleton. The study did not directly compare cheek fat volume, but it shows that visible asymmetry can also reflect differences in the bones beneath it. [3]

What we need to assess depends on whether the jaw below the ear is more prominent, the cheek looks fuller, or the tissues appear to sag farther below the jawline.

A bigger-looking side of the face does not necessarily mean there is more fat on that side.

When can Ultherapy, ONDA or fat-dissolving injections help?

First, these three treatments do not all work on the same tissue.

Ultherapy uses focused ultrasound to target tissue beneath the skin, with the aim of improving firmness and sagging. A clinical study of the lower face evaluated improvements in skin laxity around areas such as the cheeks and jawline. [4]

ONDA uses microwave energy. Depending on the handpiece and treatment area, it targets concerns such as fat tissue or skin firmness. A study using the Pocket handpiece under the chin in 10 women reported improved skin sagging. The outcome assessed in that study, however, was the degree of skin laxity under the chin. [5]

With fat-dissolving injections, the ingredients matter. Clinical trials have demonstrated that a deoxycholic acid formulation can reduce fat under the chin. That result cannot simply be applied to every “contouring injection” or to differences between the two cheeks. Both the ingredients and the treatment areas can be different. [6]

There is an important distinction here. These studies looked at improvements in sagging or fat under the chin. They did not establish how much extra treatment the bigger side needs to make both sides match.

For example, if a larger right masseter muscle makes the right jaw look bigger, doing more treatment aimed at skin or fat may leave the muscle difference you are concerned about unchanged.

Before treating the bigger side more, we need to identify which tissue difference we are trying to improve.

If the masseter is the reason, should the Botox dose differ between sides?

If a difference in masseter size contributes to the asymmetry, the botulinum toxin dose and treatment area can be planned differently for each side.

In a study of 10 people with enlargement of one masseter, botulinum toxin was injected only into the enlarged side. The volume and outward prominence around the jaw decreased afterward. This supports its potential to help when the difference comes from the masseter. [7]

Another study individualized treatment according to the thickness and shape of the masseter. There is no universal formula, though, such as giving a certain multiple of the dose to the bigger side. [8]

That is why we need to look at the jaw both at rest and while you clench your teeth. We also assess how much the muscle bulges and whether the chin itself is shifted to one side.

In fact, a study of 16 people found that the response to masseter botulinum toxin differed according to the degree of chin deviation. Those with less chin deviation had a greater reduction in lower-face volume. [9]

We need to consider both what may improve by reducing the muscle and what may remain because of the underlying skeleton.

So, rather than assuming that most facial asymmetry comes from the masseter, the first step is to work out how much a muscle difference actually contributes in your face.

Will changing a habit of chewing on one side help?

We cannot assume that changing your chewing habits alone will make your face symmetrical. But we should find out why you chew on only one side.

A study of 25 people who mainly chewed on one side because of missing teeth on the other found a thicker masseter on the chewing side. In contrast, a study using 3D facial analysis in 748 people found no clear association between preferred chewing side and facial asymmetry. [10] [11]

These findings may seem contradictory, but the participants and the outcomes measured were different. A thicker muscle on the chewing side and a whole side of the face looking bigger are not the same thing.

Another study found more balanced activity between the two masseter muscles after chewing habits were corrected. But a change in the muscles’ electrical activity does not, by itself, establish that facial shape becomes symmetrical. [12]

So, if you chew only on one side, I would first suggest checking whether there are painful or missing teeth on the other side, or discomfort in the jaw joint. Research has also found an association between missing teeth and chewing-side preference. [11]

Addressing the source of discomfort so that you can use both sides comfortably is a reasonable direction. However, I do not recommend chewing only on the opposite side or exercising the jaw by chewing gum for long periods in an attempt to make the two sides the same size.

So, how should my facial asymmetry be treated?

My answer to whether Ultherapy, ONDA or fat-dissolving injections can improve asymmetry is this: “We can consider improving differences caused by fat or sagging, but differences in muscle or bone need their own assessment.”

Having a skeletal difference does not mean cosmetic treatment cannot help at all. There may still be aspects of masseter enlargement, fat or sagging that can be improved. But changing the contour in that way is different from correcting asymmetry of the jawbone itself.

If chin deviation or a difference in the bite is pronounced, an assessment by a dentist or oral and maxillofacial surgeon may also be considered when appropriate. Please decide on the specific treatment and amount after a thorough consultation with your clinician.

At your next consultation, instead of asking, “Could you do more on the bigger side?”, you might ask:

“Which part of my face is making it look asymmetric, and how much can this treatment realistically improve it?”

References

1. Launonen AM, et al. (2023). A longitudinal study of facial asymmetry in a normal birth cohort up to 6 years of age and the predisposing factors. European Journal of Orthodontics.
2. Pinto AS, et al. (2001). Morphological and positional asymmetries of young children with functional unilateral posterior crossbite. American Journal of Orthodontics and Dentofacial Orthopedics. DOI: 10.1067/mod.2001.118627a.
3. Li J, et al. (2024). Facial asymmetry of the hard and soft tissues in skeletal Class I, II, and III patients. Scientific Reports.
4. Oni G, et al. (2014). Evaluation of a microfocused ultrasound system for improving skin laxity and tightening in the lower face. Aesthetic Surgery Journal.
5. Zappia E, et al. (2025). An innovative microwave technology for the treatment of submental skin laxity. Lasers in Medical Science.
6. Humphrey S, et al. (2016). ATX-101 for reduction of submental fat: A phase III randomized controlled trial. Journal of the American Academy of Dermatology. DOI: 10.1016/j.jaad.2016.04.028.
7. Cha YR, et al. (2013). Effect of unilateral injection of botulinum toxin on lower facial asymmetry as evaluated using three-dimensional laser scanning. Dermatologic Surgery. DOI: 10.1111/dsu.12171.
8. Xie Y, et al. (2014). Classification of masseter hypertrophy for tailored botulinum toxin type A treatment. Plastic and Reconstructive Surgery. DOI: 10.1097/PRS.0000000000000371.
9. Kim D, et al. (2020). Effect of Botulinum Toxin Injection on Asymmetric Lower Face with Chin Deviation. Toxins.
10. Dogan ME, Şahin N. (2026). Ultrasonographic assessment of the effects of unilateral mastication on the temporal and masseter muscles. Journal of Prosthetic Dentistry.
11. Heikkinen EV, et al. (2024). Chewing side preference, facial asymmetry and related factors in the Northern Finland birth cohort 1986. Acta Odontologica Scandinavica. DOI: 10.2340/aos.v83.41392.
12. Wang Y, et al. (2015). Changes of masseter muscle asymmetry due to unilateral mastication after intervention: a electromyographic analysis. Journal of Southern Medical University. DOI: 10.3969/j.issn.1673-4254.2015.04.14.