Lumps, Granulomas and Vascular Occlusion after Collagen Fillers

What kinds of problems occur after collagen-stimulating filler?

The products commonly called 'collagen injections' or 'collagen filler' are, in medical terms, collagen-stimulating (biostimulator) fillers. This article covers three active substances: poly-L-lactic acid, calcium hydroxylapatite and polycaprolactone. How these products work, who they are suitable for, the debate about massage and aftercare are explained in our article “Collagen-Stimulating Fillers”; here we focus only on the problems that can arise after the treatment.

Swelling, redness, tenderness and bruising at the needle points in the first days can occur with any injection and usually pass on their own. The most common problem specific to this group of products, however, is a lump (nodule: a firm bump that can be felt under the skin). In a review bringing together 21 studies on calcium hydroxylapatite, adverse events were reported in about 3 per cent of 5,081 treatments; the great majority of these were lumps, and most lumps could not be seen from the outside and passed on their own. The U.S. Food and Drug Administration (FDA) states that side effects such as lumps and granulomas can appear weeks, months or even years after fillers. The most serious but rare problem is the product blocking a blood vessel.

If you have one of the symptoms in the last column of the table, call 112 (or your local emergency number). What to do in the case of a sudden colour change and pain is explained step by step in our article “After Fillers: When Is It an Emergency? Vascular Occlusion and Other Warning Signs”.

An early lump or an inflammatory lump (granuloma)?

Scientific sources divide the lumps that appear after these products into two main groups. The first is non-inflammatory lumps: they are mostly noticed a few weeks after the treatment, can be felt when touched, do not hurt and usually cannot be seen from the outside. A review on poly-L-lactic acid states that these lumps are largely due to the product being prepared or placed in an unsuitable way and that most of them pass on their own.

The second group is inflammatory lumps and granulomas. A granuloma is an excessive inflammatory response of the body to filler particles (a foreign body reaction). The same review reports that true granulomas due to poly-L-lactic acid are very rare, can appear months or years later and can grow over time. An international expert consensus published in 2026 also recommends classifying poly-L-lactic acid lumps as non-inflammatory and inflammatory, and emphasises that the inconsistent use of terms in this field leads to uncertainty in treatment.

This table is a general framework; not every lump fits neatly into one of these two groups. Infection can also cause lumps and swelling; fever, warmth and discharge point in that direction. Only the physician who examines you can decide which type it is; if necessary, imaging methods such as ultrasound, and sometimes a tissue sample (biopsy), are used.

What has been reported with which substance?

• Poly-L-lactic acid: non-inflammatory lumps are the most widely known problem with this product. Granulomas have been reported very rarely; one review gives a frequency of roughly between one in ten thousand and one in a thousand.
• Calcium hydroxylapatite: the great majority of reported adverse events are lumps. The review states that about half of these lumps were seen in 'mobile' areas such as the lips. Granulomas have been reported at the level of individual cases.
• Polycaprolactone: there are fewer published data. Cases of granuloma have been reported; in a series of four cases, these appeared as firm lumps under the skin that did not hurt and were assessed with ultrasound.

In a systematic review examining granulomas related to collagen-stimulating fillers (40 studies, 117 patients), a substantial proportion of cases were associated with poly-L-lactic acid and calcium hydroxylapatite; the time until the first symptom ranged from one week to 15 years. Because this review also included a product that does not dissolve in the body, the long time periods belong mostly to that product. For problems specific to fillers that do not dissolve in the body, see our article “Complications of Permanent and Semi-Permanent Fillers”. These data are based on case reports; the true frequencies are not known with certainty.

Factors that increase the risk

• Preparation of the product: not mixing the powdered product with enough fluid and for long enough, or using it too concentrated, has been associated with collection of the product and the risk of lumps.
• Depth of placement: injecting the product too close to the surface increases the risk of lumps, especially in thin skin.
• Too much product in one spot: injecting a large amount into a small area makes collection easier.
• Area: constantly moving areas such as the lips and around the mouth, and areas with thin skin such as around the eyes, have been associated with more problems.
• Areas that are risky for the blood vessels: areas such as the bridge of the nose, between the eyebrows, the forehead and the temples are considered riskier for vascular occlusion.
• Personal characteristics: the immune response varies from person to person; in some people an inflammatory reaction can develop without a cause being found.

Most of these factors depend on the choices and technique of the physician performing the treatment. Your part is to describe all your illnesses, medicines and previous fillers and to follow the aftercare instructions. For general precautions, see our article “Reducing the Risk of Complications”.

Why do the lips and the area around the eyes need extra care?

Lips: in a long-term clinical review of 1,000 patients treated with calcium hydroxylapatite, almost all the lumps were reported to be in the lips. The systematic review of granulomas also names the area around the mouth as a high-risk area. A lump felt in the lip may also be mistaken for another condition during a dental examination; so tell your dentist too when and which product was used on your lips. For general problems with lip fillers, see our article “Lip Filler Complications”.

Eyelids and under the eyes: the skin in these areas is very thin; even a small collection of product can be felt and can become visible. In addition, the blood vessels around the eyes are connected to the vessels that supply the eye. Of the reported cases of vision loss after collagen-stimulating fillers, one developed after poly-L-lactic acid treatment around the eyes and nose, and one after treatment of the temple. For general information on fillers under the eyes, see our article “Under-Eye Filler Complications”.

Can collagen filler be dissolved? Why does hyaluronidase not work?

No, it cannot be dissolved with hyaluronidase. Hyaluronidase is an enzyme that breaks down only hyaluronic acid; poly-L-lactic acid, calcium hydroxylapatite and polycaprolactone have a different chemical structure. The FDA also states that fillers not made of hyaluronic acid can be difficult or even impossible to remove. These products are broken down by the body over time; however, this process can take months and years. How the enzyme works is explained in our article “Dissolving Filler (Hyaluronidase)”.

In some products, collagen-stimulating particles may be mixed with hyaluronic acid. In such a case, the enzyme may affect only the hyaluronic acid part; the particles remain in place. This is why it is important to know the exact contents of the product used on you.

The search for a substance that can dissolve calcium hydroxylapatite is ongoing. In a laboratory study using pig skin samples, a substance called sodium thiosulfate was shown to be able to dissolve this product; the author emphasised that larger studies in humans are needed. In humans there are only reports at the level of individual cases. The evidence is limited; today this substance should not be regarded as a 'dissolver' of proven effectiveness that takes the place of hyaluronidase.

Vascular occlusion: why is it especially important with collagen-stimulating fillers?

As with any filler, these products can accidentally be injected into a blood vessel. The FDA reports that this can lead to tissue death, vision problems, blindness and stroke. An international expert consensus on calcium hydroxylapatite also states that injection into a vessel can cause tissue loss, lasting scarring, vision problems and blindness, and that immediate intervention is needed in this situation.

In a review examining cases of vision loss related to collagen-stimulating fillers, at least 11 cases were found with calcium hydroxylapatite and 2 with poly-L-lactic acid; most of the calcium hydroxylapatite cases were associated with treatments of the bridge of the nose. Vision loss with polycaprolactone has not been published, but one case of a blocked facial blood vessel has been reported. These events are rare; even so, everyone who has filler in the face needs to know the warning signs.

With hyaluronic acid filler, the physician can try to dissolve the gel causing the blockage with the enzyme. With collagen-stimulating fillers there is no such dissolver; treatment relies on other methods aimed at supporting blood flow and protecting the tissue. This makes early recognition and seeking help without delay even more important. At the emergency department, be sure to say that the filler is not hyaluronic acid and give the name of the product.

What can your physician do? Treatment options (general information)

Treatment is planned after an examination, according to the type of lump, the product, the area and how long the symptoms have lasted. The list below is for general information only; your physician decides which option is suitable for you.

• Monitoring: most small non-inflammatory lumps that do not hurt and cannot be seen decrease over time; the physician will often first suggest waiting and monitoring.
• Camouflage: one review states that visible non-inflammatory lumps can be concealed by applying hyaluronic acid filler around them. This does not remove the lump.
• Injection of medicine into the area: for granulomas, medicines that suppress inflammation (such as corticosteroids), and sometimes medicines that slow cell growth, are used. In the systematic review, this was the most frequently used method. It can have side effects such as thinning of the skin; the amount and interval are entirely the physician’s decision.
• If infection is suspected: medicine treatments chosen and monitored by the physician.
• Surgical removal: may be considered for lumps that do not respond to other methods. The systematic review reports that granulomas often resolved with surgical removal; however, surgery also has its own risks, such as scarring.
• Referral: if necessary, assessment together with specialists in dermatology, plastic surgery, ophthalmology or infectious diseases.

There are few strong studies comparing these treatments with one another; the recommendations are largely based on case series and expert opinion. Be cautious about approaches that promise fast and certain results.

What should you do if you notice a lump?

1. If there are problems with vision or speech, loss of strength, shortness of breath or a sudden colour change in the area, call 112 without waiting.
2. If there are no emergency signs, take a photo of the lump; note when you noticed it, its size and whether there is pain or redness.
3. Contact the physician who performed the treatment; ask for, or take with you, the name of the product, the date of the treatment and the areas treated.
4. Tell your physician about any recent infection, dental treatment or vaccination.
5. If you cannot reach your physician or you do not feel reassured, you have the right to get an opinion from another physician. For the general steps, see our article “What Should You Do If a Complication Occurs after an Aesthetic Treatment?”.

What should you not do?

• Do not try to break up a lump that appears weeks later by massaging it, squeezing it or piercing it with a needle.
• Do not apply heat without consulting a physician.
• Do not use antibiotics, cortisone medicines or creams on your own.
• Do not have new filler in the same area somewhere else to hide the lump.
• Do not use 'filler-dissolving' products sold online; they have no effect on these products anyway and carry additional risks.

This content is for information only; it does not replace an examination. The assessment and treatment that suit you can only be determined by a physician’s examination.