Swelling is not a sign that something went wrong — with fat dissolving injections, it is usually the treatment doing its job.
What are the side effects of fat dissolving injections? The most common are swelling, redness, tenderness, bruising and a burning or tingling feeling at the injection site, which usually settle over days to a couple of weeks. Temporary numbness is also reported. Less common risks include nerve irritation affecting the smile, difficulty swallowing from swelling under the chin, infection and skin injury, which is why treatment should be doctor-led.
How fat dissolving injections work
Breaking down fat cells
Injection lipolysis — often called meso fat — uses an injected solution to disrupt fat cells in a small, localised area. The body then clears the debris gradually, which is why results build over weeks and why inflammation is part of the process.
Not all injections are the same
Products and ingredients vary between clinics. Deoxycholic acid, sold as Kybella, is the version approved by the US FDA for fat under the chin. Other formulations may have less published safety data, so ask your clinic exactly what is being injected and why.
Common side effects and how long they last
| Side effect | How common | Typical duration |
|---|---|---|
| Swelling | Very common, especially under the chin | Often around a week or more |
| Tenderness or burning | Common during and after injection | Hours to several days |
| Redness | Common | Hours to a few days |
| Bruising | Common | About one to two weeks |
| Numbness | Reported | Can last several weeks |
| Firmness or small lumps | Possible | Usually soften over weeks |
Typical pattern based on deoxycholic acid data; other formulations and individual responses vary.
What the evidence says about swelling and numbness
Expect the swelling
Wake Forest Baptist Health describes moderate swelling for about 10 days and mild numbness for three to four weeks after deoxycholic acid treatment, with most patients needing two to four sessions spaced about a month apart.
Why it matters on holiday
If you are visiting Koh Samui for an event or photos, plan treatment well ahead. Visible swelling under the chin is normal for several days.
Rare but important risks
A 2024 analysis of FDA adverse-event reports in PMC noted that phase 3 trials recorded temporary nerve injury to the lower lip in up to 4.3% of patients and difficulty swallowing in 1.9%. Seek prompt review if you notice:
- An uneven smile or lower lip weakness
- Difficulty swallowing or breathing — seek urgent care
- Skin that darkens, blisters or breaks down
- Increasing pain, heat or pus suggesting infection
- Hair loss in the treated area
- Hard lumps that are not softening after several weeks
Who should avoid or delay treatment
Medical reasons
Treatment is usually postponed during pregnancy or breastfeeding, with active skin infection in the area, or with certain bleeding disorders or medicines. Tell your doctor about every condition and medicine.
When fat is not the problem
Loose skin, muscle banding or a weak chin can look like a double chin. In those cases fat dissolving will not help, and skin tightening, Botox or filler may be discussed instead.
Step-by-step: reducing side effects
A sensible sequence before and after treatment:
- Have an in-person assessment to confirm the fullness is fat.
- Ask which product will be injected and how many sessions are expected.
- Tell the doctor about medicines, supplements and bleeding tendencies.
- Schedule treatment well before events, photos or flights.
- Use a cold compress gently afterwards if advised.
- Sleep with your head slightly raised for the first night or two.
- Contact the clinic promptly about smile changes, swallowing problems or skin breakdown.
How many sessions and when results appear
Gradual change
Fat reduction develops over weeks after each session as the body clears the treated cells. Several sessions are commonly needed, and the exact number depends on the area and product.
Keeping results
Fat cells that have been destroyed are generally not expected to come back, but remaining fat cells can still enlarge with weight gain, so stable weight helps maintain the outcome.
Fat dissolving at LIV Clinic
Doctor-led assessment
At LIV Clinic on Koh Samui and Koh Phangan, Dr. Narathai confirms whether fat dissolving suits your concern, explains the product used and plans sessions around your stay.
Read next
See our fat dissolving injection service, read double chin treatment without surgery, or book a consultation.
Frequently asked questions
What are the side effects of fat dissolving injections?
Most commonly swelling, redness, tenderness, bruising and a burning feeling, plus temporary numbness. Rarer risks include nerve irritation, swallowing difficulty, infection and skin injury.
How long does swelling last after fat dissolving injections?
Under the chin, moderate swelling for around 10 days is commonly described after deoxycholic acid treatment. Smaller areas may settle sooner; it varies.
Is numbness normal after fat dissolving?
Mild numbness is reported and can last a few weeks. Tell the clinic if it is spreading or affects your smile.
Are fat dissolving injections FDA-approved?
Deoxycholic acid (Kybella) is FDA-approved for fat under the chin. Other formulations vary, so ask your clinic what is being used.
Can I fly after fat dissolving injections?
Usually yes, but swelling can be noticeable for several days, so many people plan treatment earlier in their trip. Ask your doctor about your itinerary.
How many fat dissolving sessions will I need?
Commonly two to four for the under-chin area with deoxycholic acid, spaced about a month apart, though this varies by area and product.
Safety and consultation
Fat dissolving injection is a medical procedure and, like any injectable, carries some risk — common temporary effects include swelling, tenderness, bruising and numbness, and less common reactions such as nerve irritation, swallowing difficulty or skin injury are possible. Results vary from person to person, and no specific outcome can be promised. This article is general information, not medical advice.
At LIV Clinic, every treatment begins with an in-person assessment by Dr. Narathai Vichienkalayarut, M.D., who reviews your skin, medical history and goals before recommending a personalized plan. Book a consultation to find out whether this treatment suits you.
LIV Clinic — “Live Your Life Young”
Doctor-led aesthetic and wellness clinic on Koh Samui and Koh Phangan, serving both international visitors and local residents.
Koh Samui (Bophut): 1/63 Thaweeratpakdee Rd, Bo Put, Koh Samui, Surat Thani 84320 · Tel 065-996-4242
Koh Phangan: 116/16 Moo 1, Koh Phangan, Surat Thani 84280 · Tel 093-254-5259
LINE: @Livclinic · Book a consultation
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