As millions of Americans turn to blockbuster weight-loss drugs to shed pounds, some are reporting an alarming and little-known side effect – a burning sensation that leaves their skin feeling as though it’s ‘on fire.’
The phenomenon, known as allodynia, is a type of nerve pain that causes normally harmless sensations, such as clothing brushing against the skin or even the lightest touch, to become painful.
Sufferers have likened the feeling to severe sunburn, despite there being no visible redness or irritation.
Although allodynia is not currently listed as a recognized side effect of popular weight-loss injections such as Ozempic, Wegovy, Mounjaro and Zepbound, a growing number of medical reports have raised questions about a possible link.
And on social media, patients have been sharing strikingly similar experiences.
‘I have [areas] all over that are burning. It’s driving me nuts. The soft parts of my arms, lower back and creases where my legs meet my torso are on fire!’ one user wrote on Reddit.
Another commented: ‘Over-the-counter pain medications don’t help. Lidocaine [anesthetic] gels don’t help. It’s terrible.’
Some patients say the pain subsided after they reduced their dose or stopped taking the medication, raising the possibility that the reaction may be linked to the amount of drug they are taking.
Kaela has amassed more than 40,000 TikTok followers by documenting her weight-loss journey on GLP-1s
However, researchers have yet to establish whether the injections directly cause the symptoms, or how common the problem might be.
One person who has experienced these symptoms is Kaela Knight, a 25-year-old nail artist and content creator from Colorado, who has amassed more than 40,000 TikTok followers documenting her weight-loss journey.
Before starting tirzepatide in September 2024, Kaela weighed 210 pounds, having already lost 30 pounds through diet and lifestyle changes. However, she says calorie tracking had led to an unhealthy relationship with food and she regained the weight she had lost.
Her doctor ultimately recommended the medication as an alternative approach to managing her weight and explained that it could also help alleviate some symptoms of her Postural Orthostatic Tachycardia Syndrome, a condition that affects blood flow and can cause dizziness, fatigue and a rapid heart rate when standing.
Alongside the injections, Kaela focused on eating a high-protein diet, staying hydrated and developing healthier habits.
She eventually reached 125 pounds, losing a further 85 pounds.
But while she experienced some relatively common side effects, including fatigue and acid reflux, she also began suffering from a strange burning sensation across her skin when she increased her dose from 2.5 mg to 5 mg.
‘I first noticed the symptoms during my second month of treatment, particularly as I began increasing my dosage to around 5 mg of compounded tirzepatide,’ she tells the Daily Mail.
‘I always describe it as feeling like a sunburn without any visible redness or irritation. Even the lightest touch against my skin could be uncomfortable.’
The pain appeared in different parts of her body during each episode.
‘The sensations appeared in random, localized areas, including my hips, forearms, and the back of my neck.
‘On two occasions, the burning seemed to move between different areas of my body for about a week or so. Those episodes were definitely the most uncomfortable and unusual,’ she says.
Each episode typically lasted between 24 and 48 hours before disappearing.
‘The sensations didn’t significantly affect my daily activities, but they were definitely uncomfortable,’ she adds. ‘Even something as simple as clothing brushing against my skin could be irritating.’
Concerned, Kaela contacted her doctor, who told her that other patients had reported similar symptoms.
At her heaviest, Kaela Knight weighed 210lbs before starting on tirzepatide. Today, she weighs a healthy 125lbs and has shared her story with her 40,000 TikTok followers
She says she was advised to take a vitamin B supplement, although there is no established evidence that this treats allodynia associated with weight-loss medication.
‘My symptoms seemed to resolve as I lowered my dose for maintenance, which is 2.5 to 4 mg. I also learned about ways to manage the discomfort, including cool compresses and loose clothing,’ she says.
Over the course of her treatment, Kaela estimates she experienced the burning sensation around ten times.
Although the symptoms were uncomfortable, they were not severe enough to persuade her to stop taking the medication.
She hopes that sharing her experience will encourage others with similar symptoms to seek medical advice.
‘When I first shared my experience online, I thought it was extremely uncommon. I was shocked by how many people related to what I was describing.
‘Listen to your body and advocate for yourself. Everyone’s experience is different, so don’t hesitate to reach out to your healthcare provider if something doesn’t feel right.’
‘Side effects can be frustrating, but many can be managed. While not every side effect is preventable, prioritizing protein, hydration, movement, and healthy routines can make a huge difference in your overall journey,’ she says.
But what does the medical evidence tell us about this potential side effect – and could it become more common as increasingly powerful weight-loss drugs are developed?
To understand what might be happening, it helps to know how these medications work.
Drugs such as semaglutide and tirzepatide mimic the action of hormones involved in regulating appetite and blood sugar.
Semaglutide acts on receptors for a hormone called GLP-1, while tirzepatide also targets receptors for a second hormone, GIP.
Both drugs act on appetite-regulating pathways in the brain, helping people feel fuller and reducing how much they eat.
Researchers have suggested that these effects on the nervous system might also help explain why some patients experience unusual skin sensations.
‘It’s possible these medications are impacting receptors on nerves within the brain, which is their primary site of action for regulating appetite,’ says Dr Richard Siegel, an endocrinologist at Tufts Medicine.
‘These symptoms appear to be more peripheral, but effects originating in the brain can travel through the spinal cord and into the nerves, ultimately leading to symptoms such as skin sensitivity.’
Dr Siegel also suggests that changes in the layer of fat beneath the skin during weight loss could potentially affect nerve sensitivity.
‘It’s been hypothesized that changes in the layer of fat beneath the skin may contribute to abnormal skin sensation, potentially making nerves more sensitive or altering their position.
‘However, some people appear to develop symptoms sooner than would be expected from weight and fat loss alone,’ he says.
Neither theory has been proven, and researchers do not yet understand why these drugs might cause the reaction.
However, several published medical reports have described patients developing allodynia while taking them.
In an October 2025 report, researchers documented two cases involving semaglutide and tirzepatide.
The first involved a 56-year-old woman being treated for obesity who developed painful skin sensations within weeks of switching from liraglutide to a weekly 2.4mg dose of semaglutide.
Her symptoms persisted for six weeks before resolving without treatment.
The second patient, a 75-year-old man with type 2 diabetes, developed a burning sensation across his body after switching from oral semaglutide to tirzepatide.
His tirzepatide dose had been gradually increased to 15mg weekly, the highest approved dose.
The pain initially lasted two weeks before disappearing, but later returned more severely.
After he stopped taking tirzepatide and switched back to oral semaglutide, the symptoms resolved.
The researchers suggested that the reaction might be dose-related, particularly as some patients improved after reducing or stopping treatment.
However, two cases cannot establish that the drugs were responsible.
An earlier report, published in April 2025, described four patients who developed allodynia after increasing their weekly semaglutide dose to 2.4mg.
Two stopped taking the medication and their symptoms resolved.
Of the two who continued treatment, one recovered after four months, while the other briefly stopped the drug before restarting it without experiencing further pain.
These cases suggest that the symptoms may sometimes disappear without patients having to permanently stop treatment.
‘These symptoms can certainly last days to weeks,’ says Dr Siegel.
‘With many of the initial side effects seen with this class of drugs, such as nausea and constipation, the body tends to adapt over time.
‘It’s possible something similar is happening here, where temporary changes in receptor activity alter nerve signaling at first, but become less noticeable as the body adjusts.’
But although the reports raise the possibility of a genuine drug reaction, they cannot establish how frequently it occurs.
Clinical trials have, however, recorded a broader category of abnormal or unpleasant skin sensations, known as dysesthesia.
This can include burning, tingling or other uncomfortable sensations, but is not necessarily the same as allodynia, in which normally harmless touch becomes painful.
In one trial of high-dose oral semaglutide, dysesthesia was reported in fewer than three percent of 334 patients taking the drug, compared with none in the placebo group.
And there is evidence that such symptoms may be more common with some newer, more powerful weight-loss medications.
One of these is retatrutide, an experimental injection that targets three hormone receptors – GLP-1, GIP and glucagon – rather than the one targeted by semaglutide or the two targeted by tirzepatide.
In Phase 3 trial data, dysesthesia was reported in 8.8 percent of patients taking a 9mg dose and 20.9 percent of those taking 12mg, compared with just 0.7 percent of patients receiving a placebo.
Although these figures are striking, they refer to the broader category of abnormal skin sensations, rather than confirmed cases of allodynia.
The reactions were generally mild and rarely caused patients to discontinue treatment.
The findings nevertheless raise questions about whether drugs that act on more hormone pathways, or are given at higher doses, might be more likely to cause sensory disturbances.
For now, there is insufficient evidence to establish who is most susceptible.
‘As best as I can tell, it would mostly be people on higher doses of these medications,’ says Dr Siegel.
‘Otherwise, it is not clear who may be more susceptible. I might wonder if people who are more sensitive to pain – people with fibromyalgia as an example – might be more prone to this, but it’s not clear.’
For patients who develop unusual skin pain while taking weight-loss medication, doctors may consider whether adjusting the dose or switching treatment is appropriate.
However, patients should not change or stop prescribed medication without discussing it with their healthcare provider.
It is also important not to assume that any burning or painful skin sensation is caused by the injections, as allodynia can occur with other conditions, including shingles, migraines and certain forms of nerve damage.
Dr Siegel recommends keeping a record of when symptoms occur, where they appear and whether anything makes them better or worse.
‘The more information, the better. Writing down when it is happening, where, if anything makes it better or worse, or if it occurred at a particular time of day, are very important.
‘This information can be combined with the physical exam to come up with an assessment and plan.’
And while the available evidence suggests that some patients experience temporary symptoms that resolve without lasting problems, persistent or worsening pain should be assessed by a medical professional.
‘Many rare side effects are fairly benign and not worrisome. Occasionally they can be concerning,’ Dr Siegel says.
‘It’s useful to gather data so you can have an intelligent discussion with whoever is prescribing the medication.’