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Pain is the most significant factor in the experience of receiving cosmetic injections. Even when the results are favourable, many patients find the pain too much to bear and abandon the procedure. Therefore, minimising injection pain while ensuring the effectiveness of treatment has become crucial for cosmetic clinics looking to improve customer satisfaction and encourage repeat custom. For doctors, a more comfortable injection process means greater patient cooperation, a steadier workflow and an improved treatment experience. For patients, a relaxed and comfortable experience alleviates their fear of needles and enhances their trust in the doctor and the clinic.

In clinical practice, numbing creams, cold therapy, vibration and pressure are commonly used to alleviate discomfort. However, it is not possible to judge the effectiveness of these methods based on experience alone. This article compares these analgesic methods in the context of a frontalis muscle injection.

The study included 70 healthy participants aged between 20 and 60. Given that pain perception is easily influenced by individual sensitivity, participants were not simply assigned to different analgesia groups. Instead, each participant completed five comparisons within the same procedure, thereby reducing the impact of differences in pain thresholds on the results.

01.How to set up the five regions and the injection model

Both the forehead region and the injection model are key components of this controlled design. Specific settings include:
Zoning method: the forehead is divided into five equal regions. Region A is a no-analgesia control; Region B uses a topical anaesthetic; Region C uses vibration stimulation; Region D uses cryotherapy; and Region E uses pressure. This zoning method is used for intra-subject control (see Figure 1).

The injection model involves each subject receiving five consecutive 0.1 ml injections of 0.9% sodium chloride solution into the frontalis muscle to simulate a BoNT-A injection.
Needles and injection points: 30G needles (8.0 × 0.3 mm) are used. The injection points are located approximately 2 cm above the eyebrow, corresponding to the central area of each region. There is at least 3 cm between the centres of each injection area.
The depth and scope of the injections are limited to the frontalis muscle, and they are not administered into the corrugator supercilii and depressor supercilii muscles. The needle enters the skin vertically without touching the bone surface.
Procedure: The face is disinfected with a 0.2% chlorhexidine solution prior to injection. The injection sequence is fixed, starting on the right side of the forehead and working across to the left. A 3-minute rest period is observed between each injection, with a new needle used each time.
All injections are performed by the same operator in a single procedure. To minimise the impact of differences in the operator and subjective expectations on pain evaluation, subjects are unaware of the specific analgesia method used for each area.

02.How to perform the four methods of analgesia

All four methods are non-invasive, but the specific parameters differ.
①For anaesthetic cream, apply a lidocaine/prilocaine compound cream evenly to a thickness of approximately 3 mm, then cover with a transparent film and leave for 30 minutes before injection.
②Vibration: Apply a vibration device continuously for 30 seconds before and during injection. Position it approximately 2 cm above the injection site at a frequency of 6,000 rpm.
③Cold therapy: Apply a cooling device to the injection site at a temperature of 5°C for 60 seconds, or until the subject reports pain. This is more accurately described as ‘cold therapy/cooling analgesia’ than simply applying ice.
④Press: Use a pressure device to apply standardised pressure. The contact end has a flat, circular surface area of 1 cm² and applies a pressure of 1 kgf/cm² for 30 seconds, which helps to minimise interference from variations in technique.
The evaluation includes four main types of information:
– NRS pain scores during and immediately after injection
– Preference for analgesia methods when re-injecting
– Ranking of discomfort
– Whether persistent pain, bruising, redness, itching or other abnormal reactions occur within 15 days.

03.Study Conclusions

There was no significant difference in pain scores. The results of the pain score analysis were straightforward, with no statistically significant differences between the groups. The NRS scores during injection were as follows:
No analgesia: 2.46 – Numbing cream: 2.96 – Vibration: 2.80 – Cold therapy: 3.00 – Pressure: 3.46
Immediately after injection, the NRS scores were as follows:
No analgesia: 2.49 – Numbing cream: 2.89 – Vibration: 2.80 – Cold therapy: 2.99 – Pressure: 3.52

Anesthetic cream is preferred to pressure application, which is considered more uncomfortable.

In terms of discomfort, 39% of participants found anaesthetic cream to be the least uncomfortable method, while 36% found pressure application to be the most uncomfortable.
In terms of preference, 47% said they would prefer anaesthetic cream for future injections and 47% said they would least prefer pressure application (see Figure 2). Only one participant experienced bruising after the injection, suggesting that adverse reactions are uncommon.

However, it is important to note that a preference for anaesthetic cream does not necessarily equate to superiority in terms of pain scores.

All four methods are based on the same logic for reducing pain. So why didn’t the results differ significantly? Although these four methods are all based on the principle of reducing pain, they work in different ways.

Anaesthetic plaster: It affects nerve conduction by blocking ion channels on the cell membranes of neurons in the application area through local anaesthesia, thus affecting action potential transmission.

Vibration: It stimulates mechanoreceptors through mechanical stimulation, activating large-diameter Aβ fibres and disrupting the transmission of pain signals to the central nervous system.

Cold therapy: It contributes to analgesia by activating cold-stimulation-related pathways and TRPM8 channels.

Acupressure belongs to a category of mechanical stimulation or manual distraction methods that can relieve pain by promoting the release of β-endorphins.

However, the overall pain score for this simulated injection into the frontalis muscle was low. This may have been due to the needle being inserted vertically without touching the bone surface, the use of a new needle each time, the injection being confined to the frontalis muscle, and the relatively insensitive nature of the tissue in this area.

In scenarios with strict variable control, different analgesia methods may not differ in terms of score, even if they are theoretically sound.

04.The choice of clinical approach should not be based solely on methods of analgesia.

Physicians should not judge the effectiveness of frontalis muscle injection analgesia solely on the method used, but also on factors such as individual pain sensitivity, acceptability of the method, use of a new needle, needle suitability, correct performance of the injection and suitability of the outpatient procedure.

Anaesthetic plasters are more readily accepted. While pressure has an analgesic effect, this method was associated with a higher proportion of discomfort and dislike, requiring caution when using it. Furthermore, this result is based primarily on simulated frontalis muscle injections in healthy subjects and should not be directly extrapolated to individuals with abnormal pain sensitivity, or to other injection sites or scenarios. The final choice should be based on patient preference, the procedure, and the injection technique itself.

Frontalis muscle injection analgesia should not solely focus on which method is the most effective. More importantly, patient preference, operational efficiency, and injection technique should be evaluated together.

In recent years, an increasing number of innovative pain relief solutions have been adopted in clinical practice. DermEase™ is based on Gate Control Theory and the effectiveness of its non-invasive shot-blocking device for reducing the pain of in-office injections in hand surgery has been approved by the National Institutes of Health (NIH). This technique involves applying mild mechanical stimulation to the skin to activate tactile nerve fibres and inhibit the transmission of pain signals to the brain. This effectively reduces pain during injection without affecting its effectiveness.
Compared to other methods, DermEase™ is a non-invasive plastic disc that provides immediate relief without the use of drugs or chemicals, or any waiting period. 

This has been proven by the American Association for Hand Surgery. The National Institutes of Health (NIH) reported on the effectiveness of a non-invasive shot-blocking device for reducing the pain of in-office injections in hand surgery. 

To date, we have received a great deal of valuable clinical feedback from dermatologists.

-“I’ve used them and the general consensusis that it really helps.The key is to qive the “wings”a goods squeeze, don’t be afraid to be firm – it seems to work better that way
I’ll definitely use these moving forward.”

-“Could tell l was getting a needle but no pair my client told me.”

In the future, competition in the medical aesthetics industry will not only be reflected in treatment results, but also in optimising the entire treatment experience. Taking an ‘experience-oriented’ approach to make every injection more comfortable, safe and reassuring will be crucial to enhancing brand competitiveness and customer loyalty.