A patient returns months after an aesthetic injectable treatment with a new lump, swelling or inflammatory lesion.
The original procedure may have been completely uneventful. The treatment settled normally. Then something changed.
Delayed-onset nodules (DONs) are most commonly discussed in relation to dermal fillers, but emerging evidence provides an important reminder that practitioners shouldn’t automatically restrict their assessment to one product category.
A recently published case involving compounded tirzepatide described nodules at previous injection sites involving hyaluronic acid (HA), calcium hydroxylapatite (CaHA) and incobotulinumtoxinA.
That doesn’t mean GLP-1/GIP medicines cause delayed nodules. It does reinforce a much broader clinical principle:
When a patient develops a delayed reaction following aesthetic injectable treatment, practitioners need to understand what was injected, where it was injected, how the presentation has evolved and what has changed in the patient’s medical history since treatment.
What Are Delayed-Onset Nodules?
A delayed-onset nodule is a lump, area of induration, swelling or inflammatory lesion developing after the expected immediate post-treatment period.
It may appear weeks or months after treatment, including after an area seemed completely settled.
Most importantly: a DON describes a presentation. It does not provide a diagnosis.
Depending upon the treatment and clinical presentation, the differential diagnosis can include:
- non-inflammatory product-related nodules;
- delayed inflammatory or immune-mediated reactions;
- granulomatous reactions;
- infection;
- biofilm-associated processes;
- abscess formation; and
- other local tissue responses.
The appropriate response is therefore not simply: “There’s a nodule — treat the nodule.” The practitioner first needs to establish what they may actually be treating.
DONs Are Not Exclusively About Hyaluronic Acid Filler
The aesthetic injectable category now encompasses products with very different compositions and mechanisms of action.
These include conventional HA dermal fillers, calcium hydroxylapatite products, poly-L-lactic acid biostimulators and botulinum toxin treatments.
That matters because the same apparent clinical presentation does not necessarily have the same underlying pathology — or the same management options.
Hyaluronic Acid and Delayed-Onset Nodules
HA fillers account for a substantial proportion of aesthetic injectable treatments.
Professional HA ranges available through Dermal Fillers include established product families such as Restylane, JUVÉDERM and Belotero.
Where a DON involves HA, hyaluronidase may have a role in selected circumstances because it can enzymatically degrade hyaluronic acid.
But the availability of hyaluronidase should never become a substitute for assessment. An HA-associated nodule could still represent different underlying processes.
HA filler + lump does not automatically equal dissolve.
Calcium Hydroxylapatite and Delayed Nodules
Calcium hydroxylapatite is fundamentally different from HA.
RADIESSE is a CaHA injectable with volumising and biostimulatory properties. Hyaluronidase does not simply dissolve CaHA.
This distinction becomes particularly important where the practitioner assessing the complication did not perform the original treatment. A patient may simply say: “I had filler.” That isn’t enough.
The 2026 tirzepatide case is particularly relevant here because nodules were documented at CaHA as well as HA injection sites.
Poly-L-Lactic Acid and Biostimulatory Injectables
Poly-L-lactic acid products such as Sculptra work differently again.
PLLA is used for its biostimulatory effects and cannot simply be dissolved with hyaluronidase.
Nodule formation has long been an important consideration with biostimulatory injectables, making product identification, injection history and differential diagnosis particularly important.
Practitioners interested in the differences between two major biostimulatory approaches can also read Sculptra vs RADIESSE: A UK Practitioner Comparison.
What About Botulinum Toxin Injection Sites?
This is where the recent evidence becomes especially interesting.
DON literature has traditionally concentrated heavily on fillers.
However, the 2026 JAAD Case Reports case described nodules not only at HA and CaHA sites but also at previous incobotulinumtoxinA injection sites, including nodules at the glabella.
That doesn’t establish that botulinum toxin routinely produces the same delayed nodule phenomenon as filler. Nor should evidence from a single case be generalised to all toxin products.
But it does mean that when a patient develops multiple delayed facial nodules, the practitioner should establish the patient’s complete aesthetic injection history rather than only asking about filler.
The First Assessment: What Was Injected and Where?
A systematic treatment history should establish, where possible:
- every injectable product used;
- whether it was HA, CaHA, PLLA, botulinum toxin or another material;
- brand and specific product;
- treatment dates;
- anatomical sites;
- volumes or doses;
- treatment technique where relevant;
- whether different products were used in the same anatomical region; and
- whether previous treatments had been tolerated normally.
Where another clinic performed the treatment, obtaining the treatment records may substantially improve the assessment.
Is the Nodule Inflammatory or Non-Inflammatory?
The next major distinction is the clinical presentation.
A patient may present with a small, painless, non-inflammatory lump. Another patient may present with erythema, warmth, pain, tenderness, oedema, induration, fluctuance, discharge, recurrent episodes, multiple lesions or systemic symptoms.
These aren’t interchangeable presentations. Practitioners should examine and assess the patient rather than applying a standard “nodule protocol” to every case.
Could the Nodule Represent Infection?
Potentially.
Infection forms part of the differential diagnosis of delayed complications following aesthetic injections.
Not every inflammatory nodule is an infection. Equally, not every inflammatory nodule should automatically be assumed to be sterile.
The distinction becomes especially important where there is progressive pain, erythema, warmth, fluctuance, discharge, significant swelling or systemic illness.
A suspected abscess requires a different clinical approach from an uncomplicated non-inflammatory nodule.
Where Does Biofilm Fit?
Biofilm-associated infection has been discussed extensively in the filler-complication literature.
But practitioners should be careful about using “biofilm” as a default explanation whenever a delayed nodule cannot immediately be explained. The infectious differential needs appropriate clinical consideration.
Interestingly, the authors of the 2026 tirzepatide case acknowledged that infectious causes couldn’t be completely excluded because the nodules weren’t biopsied. They considered the distribution, clinical history and behaviour of the lesions more suggestive of an inflammatory reaction.
That limitation matters. A subsequent academic discussion specifically addressed the inflammatory interpretation of these nodules, illustrating that the mechanism remains an area of active discussion rather than settled science.
When Can Ultrasound Help?
Ultrasound is increasingly useful in aesthetic complication assessment.
Where appropriate, imaging may help determine:
- where filler material is located;
- its relationship to a palpable lesion;
- characteristics of surrounding tissue;
- whether a fluid collection may be present; and
- whether intervention or further investigation may be appropriate.
Ultrasound isn’t necessary for every nodule. But it can be valuable where the treatment history is uncertain, multiple materials may have been injected, the clinical diagnosis is unclear or a collection is suspected.
What Has Happened Since the Original Treatment?
This question is easily overlooked.
The original consultation tells you about the patient when the injectable treatment was performed. A DON may appear months later.
During that period the patient may have experienced infection, illness, vaccination, dental treatment, newly diagnosed medical conditions, new medicines or changes to existing medication.
Delayed inflammatory reactions involving established filler sites have previously been reported following systemic events.
The FDA has also noted reports of inflammation near dermal filler sites following viral or bacterial illness or infection, vaccination and dental procedures.
The practitioner therefore needs an updated medical history, not merely the original treatment record.
Where Do GLP-1/GIP Medicines Enter the Picture?
This is the emerging part of the story — not the definition of DONs.
The overlap between people receiving aesthetic injectable treatments and those receiving medical weight-management treatment is increasing rapidly.
In March 2026, Moore and colleagues reported persistent facial nodules in a patient who had started compounded tirzepatide.
Nodules occurred at sites treated with HA filler, CaHA filler and incobotulinumtoxinA.
The authors reported that new nodules ceased after compounded tirzepatide was stopped and subsequently recurred after rechallenge and dose escalation. They nevertheless explicitly acknowledged limitations including the unknown composition of the compounded preparation, absence of biopsy and inability to establish causation.
That’s exactly the level of caution practitioners should maintain.
What About Semaglutide?
The discussion isn’t limited entirely to tirzepatide.
A recent dermatological review describes a reported case of delayed facial oedema and inflammatory reaction occurring after HA filler treatment following initiation of semaglutide.
Again, an individual case doesn’t establish a class effect. It adds to the reason for practitioners to ask about new weight-management medicines when taking the history of an unexplained delayed reaction.
Does GLP-1/GIP Treatment Cause DONs?
We don’t currently know.
The evidence isn’t sufficient to establish causation, incidence, relative risk, a class effect, which patients may be susceptible, whether particular injectable materials carry greater risk, or whether medication dose or duration changes risk.
And the 2026 report specifically involved compounded tirzepatide, which adds another important limitation when trying to extrapolate its findings to licensed tirzepatide products generally.
GLP-1/GIP medication belongs in the history. It does not currently belong in the diagnosis.
The Longeva Wellness Perspective
This article is about DONs and aesthetic injectable complications from the practitioner’s perspective.
Longeva Wellness separately examines the emerging question from the medical weight-management perspective, including observations encountered in clinical practice.
Read: GLP-1 Weight-Loss Treatment and Previous Dermal Filler: What We’ve Seen in Clinical Practice.
Should Practitioners Automatically Use Hyaluronidase?
No.
Hyaluronidase is relevant to HA. It isn’t a universal treatment for delayed nodules.
Before considering treatment, establish:
- What product is involved? HA, CaHA, PLLA, toxin or another injectable?
- What is the clinical presentation? Inflammatory or non-inflammatory?
- Is infection possible? Are there clinical features suggesting infection or abscess?
- Would investigation help? Would ultrasound, microbiology or another assessment change management?
- Is intervention appropriate? Or is referral or further investigation the safer course?
This distinction is particularly important when several different injectable materials have been used.
What About Antibiotics or Corticosteroids?
Management should follow clinical assessment and the suspected pathology.
Where infection is suspected, appropriate antimicrobial management may be required following assessment and prescribing by an authorised healthcare professional.
A collection or abscess may require additional investigation or intervention.
Indiscriminate antibiotic treatment of every delayed nodule is inconsistent with antimicrobial stewardship.
Corticosteroids also require appropriate clinical judgement, particularly if infection hasn’t been adequately considered.
Longeva Aesthetics supplies non-POM aesthetic products. Prescription-only medicines require an appropriate prescribing and regulated pharmacy pathway.
When Should a Practitioner Escalate?
Consider referral, escalation or specialist input where:
- the diagnosis remains unclear;
- the injected product is unknown;
- several different materials may be involved;
- infection or abscess is suspected;
- symptoms are severe or progressing;
- systemic symptoms are present;
- imaging or microbiological investigation is required;
- previous management has failed; or
- the presentation falls outside the practitioner’s competence.
Knowing when not to intervene is an important part of complication management.
A Practical DON Assessment Framework
- Identify every injectable treatment. Don’t ask only about filler.
- Establish the product and material. HA, CaHA, PLLA, botulinum toxin or something else?
- Map the injection sites. Do the nodules correspond with previous treatment locations?
- Establish the chronology. When was each treatment performed and when did symptoms begin?
- Examine the presentation. Inflammatory or non-inflammatory?
- Consider infection. Look for clinical features that change the urgency and management pathway.
- Update the medical history. What happened after the original injectable treatment?
- Review medication changes. Including semaglutide, tirzepatide and other recently started or changed medicines.
- Consider investigation. Would imaging, microbiology or another assessment improve diagnostic confidence?
- Treat the suspected pathology — not the word “nodule”. Management depends on what the practitioner believes is actually occurring.
- Work within competence. Recognise when specialist input is appropriate.
The Key Message About Delayed-Onset Nodules
Delayed-onset nodules shouldn’t be reduced to a dermal filler problem.
Different aesthetic injectables can be involved in delayed reactions, and the emerging literature provides another reason to take a complete injectable and medical history.
The 2026 tirzepatide case is particularly interesting precisely because the lesions weren’t restricted to one filler type: they appeared at HA, CaHA and incobotulinumtoxinA injection sites.
That doesn’t establish that tirzepatide caused them. It does demonstrate why a patient presenting with delayed facial nodules deserves a broader assessment than: “Which filler did you have?”
Instead ask: What was injected? Where? When? What does the lesion look like? Could infection be involved? What has changed medically since treatment? Have new medicines been started or doses changed? Is investigation required? And is this within my competence to manage?
DONs are a presentation. The practitioner’s job is to work out what may be behind them.
References
- Moore L, Hurley K, Moore A. Facial nodules following filler injections after initiating compounded tirzepatide use. JAAD Case Reports. 2026;72:1–3. doi:10.1016/j.jdcr.2026.03.042.
- Moore LC, Hurley K, Moore AY. Inflammation-mediated facial nodules to compounded tirzepatide. JAAD Case Reports. 2026;75:215. doi:10.1016/j.jdcr.2026.06.026.
- U.S. Food and Drug Administration. Dermal Fillers (Soft Tissue Fillers). Safety information concerning dermal filler treatment and inflammatory reactions.
- Artzi O, et al. Delayed inflammatory reactions to hyaluronic acid fillers: a literature review and proposed treatment algorithm. Clinical, Cosmetic and Investigational Dermatology. 2020;13:371–378.
Professional disclaimer: This article is intended for educational information for healthcare and aesthetic professionals. It does not establish that semaglutide, tirzepatide or GLP-1/GIP medicines cause delayed nodules following aesthetic injectable treatment. It does not replace individual clinical assessment, diagnosis, prescribing decisions or specialist advice. Practitioners should work within their competence and applicable professional standards.