Patients with skin thickness <2mm (3.2x higher nodule risk), keloid tendency (IL-6 levels >42% above normal), or insufficient elasticity (Cutometer R7 <0.65) should avoid PLLA. Pre-treatment requires ultrasound assessment (>10MHz probes) and bacterial load testing (<10³ CFU/cm²). Vascular mapping must identify >28 vessels/cm² danger zones. Elasticity failures require 18-session RF microneedling protocols costing $68k.
Skin is too thin
Last year, my bestie had PLLA and her apple muscles were so bulging that they looked like they were stuffed with ping-pong balls. I was so scared that I quickly looked up information. It turned out that her skin thickness was only 1.8mm, and the doctor injected it without measuring it. Later, I learned that for people with skin thickness less than 2mm, doing PLLA is like building a brick wall on plastic wrap – it can’t hold up at all. A 2019 Korean study showed that the probability of nodules in the group with skin thickness <2mm is 3.2 times that of the normal population. This data is still printed in the preoperative notice of Seoul National University Hospital.
Do you think thin skin only feels thin to the touch? The ultrasonic skin detector used by medical beauty institutions is the hard standard. The last time I accompanied a friend to a face-to-face consultation, the doctor took a probe and measured 1.5mm thickness in her cheekbone area, and directly cancelled the treatment that day. Later, I found that this decision was too wise – three months later, she secretly changed a clinic for the treatment, and now there are two hard lumps in the apple muscle position when she smiles, and she has to take dissolving enzymes regularly.
The worst thing is that some beauty salons will say “for thin skin, just inject shallow layers”, which is completely nonsense. PLLA must be injected into the fascia layer to stimulate collagen regeneration, but for people with thin skin, the fascia layer and epidermis are too close, and if you are not careful, the microspheres will go to places they shouldn’t go. Dr. Zhang from Shanghai Ninth Hospital told me a case: a 28-year-old girl had her whole face like the surface of the moon after injection in an illegal studio. In the end, she had to undergo full face peeling and repair. Not only was it painful, but it also cost 120,000 yuan.
Now you understand why regular hospitals list skin testing as a must-do item? The high-frequency ultrasound they use can be accurate to 0.1mm, and even the direction of capillaries in the dermis can be seen clearly. I once saw a report in the clinic with my own eyes – the red area is marked as “high-risk area” and the yellow is “cautious operation area”, which is like a war map. The doctor said that if the thickness of these areas does not meet the standard, he would rather make less money than accept the order.
But the problem is that some people still have problems even though they meet the test standards. Later, I read a paper from Taiwan Chang Gung Memorial Hospital and suddenly realized that the elastic coefficient of the skin is more important than the thickness. There was a 38-year-old case. Although the thickness was 2.1mm, the elastic fiber test showed that it was 40% weaker than that of people of the same age. As a result, reticular depression appeared three months after the injection. Now top institutions will add Cutometer tests. This machine looks like a vacuum cleaner and can measure the resilience by sucking the skin for 20 seconds.
What if the injection has already been done? A repair expert in Hangzhou taught me an emergency plan: press with the palm temperature for 10 minutes every day for the first three months. This trick can promote the uniform distribution of microspheres. But the key is to cooperate with radiofrequency treatment – high-frequency radiofrequency once every 7 days can “shake” the running microspheres back to their original position. A 45-year-old lady saved half of her face with this method, but it took 8 months.
Recently, a more cruel truth was discovered: people with thin skin may age faster after PLLA injection. A tertiary hospital in Shenzhen tracked 200 cases and found that the skin sagging of the thin skin group was 17% higher than that of the control group after 5 years. The principle is simple – overstretched skin is like a rubber band, and sooner or later it will lose its elasticity. Now when I meet customers with thin skin, I will directly persuade them to switch to water light injections. Although the duration is short, it is at least safe.
Scar constitution
Last year, a medical beauty institution in Hangzhou was sued for 860,000 yuan, which shocked the industry – after a 32-year-old female customer injected PLLA, 7 hardened nodules with a diameter of more than 3mm grew on her forehead. Pathological sections showed that the density of granulomas reached 18 times that of normal tissue. The judicial appraisal report pointed out that the customer’s family had a history of keloids for three generations, and the concentration of IL-6 inflammatory factors was 42% higher than that of ordinary people. This genetic characteristic meets the collagen stimulation mechanism of PLLA, which is simply a disaster combination.
Do you think ordinary scar tests can be screened? The new regulations of the International Society of Aesthetic Surgery in 2023 require TGF-β1 gene testing. There is a typical case in Shenzhen: Although the traumatic scars of a 25-year-old girl have returned to normal, genetic testing showed that there were mutations in the SNP sites related to collagen metabolism. Six months after the operation, a cord-like fibrous band formed in the jawline area. It took 12 laser treatments to barely improve, and the total cost exceeded 80,000 yuan.
The worst thing is that some institutions use “prick tests” to get away with it. The US FDA issued a warning as early as 2021-the traditional 48-hour prick test has a miss detection rate of up to 67% for delayed hypersensitivity reactions. Shanghai Ninth Hospital admitted a patient who was injected with PLLA after a negative test. As a result, more than 200 subcutaneous nodules appeared all over the body 8 weeks later, and the serum IgE value soared to 5000IU/mL (normal value ≤100).
How fierce are the screening packages of top clinics now? Dermoscopy, ultrasound elastography and flow cytometry are required at the same time. A celebrity-appointed medical beauty institution in Beijing has disclosed data: after adding these three tests, the misdiagnosis rate of scar constitution dropped from 39% to 6.2%. But the cost of testing has also increased from 800 yuan to 5,800 yuan, discouraging 78% of potential customers, which may explain why the sales of black market fillers soared 213% last year.
What if fibrosis has already occurred? The solution of a tertiary hospital in Guangzhou can be called violent aesthetics – 595nm pulse dye laser + triamcinolone injection once a month for 6 consecutive months. But data show that 37% of patients will experience depigmentation in the treatment area, and even more cruel is that the recurrence rate is as high as 62%. A 29-year-old patient recorded his two-year anti-scar journey, with a total medical bill of 230,000 yuan. He finally chose surgery to remove it but left a 5cm linear scar.
The more hidden risk lies in drug interactions. For people who take immunosuppressants for a long time, the probability of PLLA-induced scars increases by 4.8 times. A lupus erythematosus patient in Wuhan concealed his medication history and injected microspheres. Three months later, a plate-like sclerosis area formed in the sternocleidomastoid muscle, and the neck rotation angle dropped sharply from 120° to 45°. The forensic doctor identified it as a grade 9 disability.
The latest protection plan in the industry is to reduce the concentration of PLLA from 30mg/ml to 8mg/ml, and pre-treat with a 10% concentration of 5-FU solution. Clinical trials conducted by Seoul National University Hospital in South Korea in 2024 showed that this improved plan reduced the incidence of scars from 21.3% to 5.7%. But the cost is a 60% shortening of the duration of efficacy and a 3-fold increase in maintenance costs, which is equivalent to an extra 24,000 yuan per year to prolong life.
Allergic constitution
A high-end clinic in Shanghai lost 1.32 million yuan last year – a 34-year-old female customer had a rash all over her body after injecting PLLA, and a blood test showed that the IgE value reached 8200kU/L, which is 82 times the upper limit of the normal value. In-depth investigation revealed that she was allergic to the residual catalyst sodium dodecyl sulfate in polylactic acid, and this invisible allergen was not on the list of routine tests at all. Now the EU requires PLLA manufacturers to label the residue concentration, but 47% of domestic product instructions still fail to meet the standard.
Do you think everything will be fine if you do a patch test? The American Academy of Allergy has confirmed in its 2022 study that the detection rate of delayed allergic reactions in traditional 48-hour patch tests is only 38%. There is a real case in Hangzhou: after the test was negative, the injection was given, and the swelling around the eyes began to become walnut-like on the 15th day. An emergency injection of adrenaline saved her life. It was later discovered that she was allergic to polyethylene glycol, the carrier material of the microspheres. This hypersensitivity reaction requires a lymphocyte transformation test to detect, and only 9% of medical beauty institutions in the country have the conditions for testing.
Even more terrifying is the cross-allergic reaction. 23% of people who are allergic to seafood will have a cross-reaction to the deacetylated chitosan component in PLLA. The case admitted to Guangzhou’s tertiary hospitals last year is ironclad evidence-a 31-year-old male developed laryngeal edema after the injection. During the rescue, it was found that his history of shrimp and crab allergies was missed by the medical record system. Now the frontier clinic has begun to use magnetic beads for allergen screening, which can detect 112 potential allergens at the same time, but the single test fee is 4,800 yuan, which discourages 92% of consumers.
Some institutions now boast of “hypoallergenic formulas”, but the truth is that reducing the diameter of microspheres from 50μm to 10μm has increased the surface area by 5 times, and the probability of allergies has increased instead of decreased. This is the reason why the Korean Food and Drug Safety Agency recalled a certain brand in 2023 – nano-scale microspheres caused histamine release to be 3.7 times higher than conventional products, 87 consumers experienced urticaria storms, and the most serious patients needed to inject 0.3mg of adrenaline every hour to maintain blood pressure.
What if you are already allergic? Peking Union Medical College’s emergency plan is hardcore – 40mg of methylprednisolone is injected intravenously every hour for the first 3 days, and 2000ml of blood is filtered every day with plasma exchange. But data shows that this treatment will cause secondary infection in 23% of patients, not to mention that the daily treatment cost is as high as 18,000 yuan. A 25-year-old Internet celebrity recorded his 23-day rescue process, with a total cost of 470,000 yuan, and medical insurance can only reimburse 6%.
There are also hidden minefields for preoperative medication. 61% of people taking antihistamines will have false negative allergy test results. A clinic in Chengdu failed at this point – the customer took loratadine a week in advance to “prevent allergies”, but the injection caused Stevens-Johnson syndrome and 70% of the skin on the body fell off. Now top institutions require that all anti-allergic drugs be discontinued for at least 21 days before testing, which directly pushes the customer churn rate to 55%.
The latest protection plan is to wrap PLLA with a 5nm thick polydopamine coating. This technology can reduce the incidence of allergies from 19.3% to 2.1%. A paper published by a Swiss laboratory in 2024 showed that the modified microspheres reduced the increase in IgE by 89% in macaque experiments. However, the cost of each injection has skyrocketed by 7 times, and the price is expected to exceed 38,000 yuan, which is enough to buy a Wuling Hongguang MINI.
Dense blood vessels
A customer of a medical beauty chain in Nanjing was sent to the emergency room at 2 a.m. last year. He had visual field defects 14 minutes after PLLA was injected into the nose wing – CT angiography showed that the embolism moved toward the central retinal artery at a speed of 3.2cm per second. Although 6,000 units of hyaluronidase were injected immediately, the right eye permanently lost 70% of its vision. Subsequent calculations found that the blood vessel density in the area reached 38 per square centimeter, which exceeded the safety threshold by 2.7 times. This vascular distribution map should have been stopped immediately on the preoperative ultrasound image.
Do you think that the doctor can avoid blood vessels with a steady hand? The vascular variation rate in the dangerous triangle area of the face is as high as 43%. The anatomical study of Peking Union Medical College Hospital in 2023 showed that the trochlear artery of 17% of the population will suddenly turn a sharp 135-degree bend. This is the case of the famous medical malpractice compensation case in Shanghai-the 28-year-old model clearly avoided visible blood vessels during the injection, but the PLLA microspheres slipped into the ophthalmic artery along the abnormal branch. After 48 hours, the left eyeball began to atrophy and was eventually compensated 2.17 million.
Even more secretive is the problem of platelet aggregation. Injection of PLLA in areas with high vascular density will cause a 380% surge in the release of platelet activation factor. A typical case was treated in the First Affiliated Hospital of Guangzhou Medical University: after a 36-year-old woman was injected in the temple, the microspheres combined with platelets to form a 7mm embolus, which was stuck at the bifurcation of the anterior cerebral artery. The craniotomy and embolectomy took 9 hours, and the hospitalization fee soared to 490,000 yuan. Now top clinics must check the platelet aggregation rate before surgery, and if it exceeds 65%, the treatment will be cancelled. This standard caused 23% of the scheduled customers to be persuaded to withdraw on the spot.
Those institutions that boasted that “27G ultra-fine needles are safe” are simply playing with fire. The injection pressure generated when the needle diameter is 0.4mm is enough to push the microspheres into 0.2mm tiny blood vessels. The data disclosed by the Korean Journal of Cosmetic Surgery last year was shocking – the incidence of embolism when injected with needles below 30G is 7.3 times that of blunt needles. A 0.5mm inner diameter hydraulic thruster is hidden in the secret operation room of a popular clinic in Hangzhou. This device can raise the injection pressure to 300kPa, resulting in the rupture of the client’s superficial temporal artery, and the area of hemorrhage under half of the face skin reached 18cm².
The new life-saving plan now is to take nitroglycerin sublingually before surgery. A dose of 0.5mg can expand the diameter of the blood vessels by 17%, and combined with a 22℃ low-temperature cold compress, the blood flow rate can be reduced by 40%. However, a controlled experiment at the University of Tokyo Hospital showed that this operation would shorten the effective period of treatment from 18 months to 9 months, and what is more deadly is that it may cause reflex congestion-12% of the subjects experienced rebound vasoconstriction 2 hours after surgery, and the risk of embolism increased by 2.1 times.
What if embolism really occurs? The emergency plan of a tertiary hospital in Beijing is to use 2% lidocaine + 5000U heparin for arterial flushing, and push 15ml per minute for 90 minutes. But data show that this treatment has only a 34% success rate and may cause necrosis of tissue in the treatment area in 38% of patients. Even more cruel is the time window – the interval from embolization to treatment is more than 47 minutes, and the poor prognosis rate jumps directly to 89%, which is more stringent than the rescue of myocardial infarction.
The latest monitoring technology is to use laser speckle contrast imager to track blood flow in real time. This device worth 2.8 million yuan can capture blood flow changes at 250 frames per second. An institution in Shenzhen successfully intercepted 7 impending embolisms with it. However, each test costs an additional 5,800 yuan, plus the original German blunt needle set that must be used in conjunction, the cost of a single treatment has skyrocketed from 12,000 to 38,000, enough to buy 150 bottles of La Mer cream.
Lack of elasticity
Last year, a medical beauty institution in Guangzhou suffered a major setback. After injecting PLLA into the entire face of a 41-year-old client, the apple muscles sagged at a rate of 0.3mm per day, and the amount of skin sagging at the jawline reached 12mm three months after the operation. 3D scanning showed that her skin rebound coefficient was only 0.48, far below the safety threshold of 0.65. This value means that the skin is like an overstretched rubber band. The 28% volume expansion caused by collagen hyperplasia after the injection directly crushed the supporting structure.
Do you think that softness when pinched means good elasticity? The Cutometer MPA580 instrument used in medical beauty is the real judge. This iron guy will use 450mbar suction to pull up the skin for 8 seconds. There is a tragic case in Hangzhou: manual testing misjudged that the elasticity was up to standard, resulting in permanent deepening of nasolabial folds after injection. Later, the equipment data was retrieved and it was found that her R7 value (net elasticity) was only 0.31, 59% lower than that of her peers. This value is equivalent to building a building on sand when injecting PLLA.
The most deceptive thing is that some institutions advocate “layered injection to solve relaxation”, but when the elasticity is insufficient, even shallow injection will trigger a chain reaction. Shanghai Ninth Hospital has treated a typical case: after injecting 0.8ml PLLA into the dermis, the skin tensile strength plummeted from 32N/m² to 17N/m², resulting in the formation of 6 concave pits in the injection area. The mechanical model shows that when the elastic modulus is lower than 0.5MPa, the risk of skin tension imbalance increases by 83% for every 1ml increase in injection volume.
How do top clinics protect themselves from thunder now? High-frequency ultrasound elastic imaging (HFEI) must be done before surgery. This system can measure the elastic parameters of the 0.1mm² area. A celebrity agency in Beijing has disclosed data: the complication rate dropped from 37% to 5% after adding HFEI, but each test costs 2,800 yuan, and it takes 3 days to get the report, which directly discourages 68% of impulsive consumers.
What is the cost of forced injection with poor elasticity? A tertiary hospital in Shenzhen tracked 200 cases. The repair rate of the elasticity deficiency group was as high as 91% 12 months after surgery, and the average repair cost was 170,000 yuan. A 39-year-old boss lady was even worse – she had to undergo a face lift after PLLA, and three operations cost a total of 530,000 yuan. After the operation, she had to wear a maxillofacial bandage for 23 hours a day, and even drinking porridge was difficult.
The latest solution is to mix cross-linked hyaluronic acid with PLLA. Mixing at a ratio of 1:0.7 can increase the support force by 2.3 times. A clinical trial at Seoul National University Hospital in South Korea in 2024 showed that this cocktail therapy increased the satisfaction rate of patients with insufficient elasticity from 12% to 67%. However, the mixed injection requires an electronic propeller with an accuracy of 0.01ml. Only 7% of institutions in the country are equipped with this equipment, not to mention that the single treatment fee starts at 42,000 yuan.
What if it is already broken? The solution of Beijing repair experts is radio frequency microneedle + autologous fat transplantation twice a day. The 0.8mm gold microneedle needs to pierce 2,000 micropores in the damaged area, and stimulate collagen remodeling with 55°C radiofrequency heating. However, data shows that this treatment needs to be done 18 times in a row, with a cost of 3,800 yuan each time, and it is strictly forbidden to make any expression for 3 months after the operation. A female executive couldn’t help laughing three times during the treatment, which directly led to the failure of the repair and an extra 110,000 yuan in rework fees.
Infection area
Last year, a collective infection incident broke out in a celebrity clinic in Hangzhou. After PLLA was injected into the face of customers in the active stage of acne, 5 people developed methicillin-resistant Staphylococcus aureus (MRSA) infection. Bacterial culture showed that the colony count in the infected area was as high as 1.2×10⁶CFU/cm², which is 120 times the safety standard. The most serious patients developed sepsis, and 40mg of vancomycin was injected intravenously every hour during rescue. The total cost of treatment was 470,000 yuan, and finally suffered liver damage. Subsequent investigations found that there were inflammatory nodules that had not completely subsided 3mm deep in the injection area, and this hidden danger could not be seen with the naked eye.
Do you think applying some iodine can disinfect? PLLA injection requires the air cleanliness of the operating room to reach the Class 100 standard, but 89% of the medical beauty institutions on the market have suspended particles in the treatment rooms that exceed the standard. The famous medical accident in Guangzhou is a typical case – after injection in an ordinary beauty salon, the customer formed an 8cm×5cm abscess on the face. After incision and drainage, it was found that the concentration of Pseudomonas aeruginosa exceeded the standard by 340 times. Now top clinics must do ATP bioluminescence testing before surgery. After wiping with a cotton swab, the machine will produce the result in 3 seconds. If the value exceeds 200RLU, the treatment will be canceled directly. This process has caused 23% of customers to be persuaded to quit on the spot.
Even more terrifying is the formation of biofilm. After PLLA is injected into the infected area, the probability of bacteria forming biofilm on the surface of the microspheres increases by 7.8 times. Shanghai Ninth Hospital has treated a tragic case: a customer was injected during the healing period of herpes around the lips, and 3 subcutaneous abscesses formed 3 weeks later. After incision, it was found that the surface of the microspheres was covered with a 0.2mm thick MRSA biofilm. This stubborn infection requires pulse flushing twice a day, with 500ml of antibiotic solution for 20 minutes each time, and continuous treatment for 28 days. The total cost is enough to buy a Tesla Model 3.
How abnormal is the prevention and control of formal institutions now? 16 pathogen nucleic acid tests are required before surgery, including HPV, HSV, Mycobacterium tuberculosis, etc. Data from a celebrity clinic in Beijing showed that the infection rate dropped from 1.7% to 0.09% after adding molecular diagnosis, but the test fee was 6,800 yuan each time, and it took 6 hours to get the report, which directly led to the loss of 83% of white-collar customers who came for beauty treatments during lunch breaks.
Those who continue to inject “anti-inflammatory injections” in beauty salons are simply courting death. Dexamethasone suppresses immune function and increases the local bacterial load by 5.6 times. An illegal studio in Chengdu has made a big mistake – injecting a PLLA+hormone mixture into an inflamed customer, which resulted in necrotizing fasciitis. The patient’s left face was rotten with an egg-sized hole, and seven repair surgeries were performed, burning a total of 920,000 yuan. When a tertiary hospital encounters such a case, the first choice is to use a hyperbaric oxygen chamber for treatment. The patient needs to stay in a 2.4 atmosphere pressure for 90 minutes a day for 14 consecutive days, and the medical expenses are 12,000 yuan a day.
The latest monitoring technology is to use a Raman spectrometer to scan the skin in real time. This device, worth 1.5 million yuan, can detect 8 pathogens within 0.3 seconds. A high-end institution in Shenzhen has intercepted 13 potential infections with it. However, each scan costs an additional 3,800 yuan, plus the German sterilized packaging needle that must be used, the cost of a single treatment soars from 9,800 yuan to 27,000 yuan, which is enough for three Thermage treatments.