Needle moxibustion: choosing the right equipment

The warm-needle technique (needle moxibustion) rests on a balance between safety, thermal conduction and clinical efficacy. The choice of equipment directly influences the quality of thermal stimulation and the associated risks. This article offers an analysis based on available scientific data.

1. Silicone: a debated safety profile

A 2010 study concluded that silicone-coated needles are biologically safe in moxibustion. However, its experimental conditions diverge from real clinical practice:

• Moxa was not applied directly to the handle
• Measured temperatures did not exceed 111°C
• No analysis of silicone degradation at high temperatures

In practice, temperatures are significantly higher, which limits the scope of these conclusions.

Source: The Biological Safety of Stainless Steel Needles Used in Warm-Needling (2010)

2. Why to avoid silicone coating

During needle moxibustion, the handle can reach 400 to 700°C, with approximately 310 to 320°C at the handle/shaft junction.

Medical silicone generally resists up to approximately 185–230°C in continuous use. Since this limit is exceeded, several phenomena may be expected:

• Thermal degradation of the material
• Release of microscopic residues
• Emission of potentially irritating fumes

These risks remain theoretical in this specific context, but are based on known physicochemical data.

Source (warm-needling temperatures): On the Hazard Caused by the Heat of Acupuncture Needles in Warm Needling (2013)

Source (silicone): Silicone Biomaterials: History and Chemistry (2004)

A clinical case (2020) reports a cutaneous granuloma linked to the presence of silicone, appearing several years after acupuncture sessions. Although rare, this type of reaction underlines the value of limiting potentially residual materials.

Source: Periorbital Silicone Granulomatosis 30 Years after Acupuncture (2020)

3. What the microscope reveals: the 2022 Korean study

In 2022, Korean researchers from the Korea Institute of Industrial Technology and Gachon University examined 285 disposable acupuncture needles. They came from 23 brands and 11 manufacturers, all sold in South Korea in 2021: 18 brands were made in South Korea and 5 in China. The researchers observed the tip of each needle under an electron microscope at 500× magnification, then analysed its chemical composition at 2,000× magnification.

The results are clear:

• 252 of the 285 needles, or 88.4%, had at least one defect. Of these, 86.9% had two or more.
• The most common defects were scratches and bumps on the surface (68.1%), peeling coating (63.2%) and lumps of material (61.8%). 71 needles had a blunt tip, and 51 a bent tip.
• For eight brands, the researchers did not find a single defect-free needle. Even the two best brands had only about half of their needles free of defects.
• Sound tips were made of stainless steel: iron, chromium and nickel. Defective tips, on the other hand, contained a lot of carbon, silicon and oxygen, the components of the silicone that coats the needles. The authors see this as the trace of an incomplete or peeling coating.

The researchers point out that a rough or blunt needle can cause pain, bleeding or bruising at the puncture site. They also note that silicone coming off the needle can be deposited on the skin and cause skin reactions. Finally, they stress that the current Korean standard only requires inspection at 10× magnification, which does not reveal these defects.

What we at Vert Nature take from it

For us, this study confirms that silicone-coated needles should be avoided, for two reasons.

First, the silicone does not stay on the needle: it peels off on nearly two needles out of three. Some of it may be deposited on the skin, but above all, since the needle passes through the skin, silicone that comes off can remain inside the body, in the tissues. The 2020 clinical case cited above shows this: a silicone-related granuloma appeared years after acupuncture sessions. In needle moxibustion, the silicone is also subjected to temperatures far above what it can withstand, as we saw above.

Second, the silicone is there to make the needle glide. On a poorly finished, scratched or blunt-tipped needle, it smooths the insertion and makes these manufacturing defects much less noticeable, for the practitioner as well as for the patient. A well-sharpened, well-polished needle does not need this artifice. Choosing an uncoated needle means choosing a needle whose quality cannot hide.

Source: Park DY et al., Morphological and Chemical Analysis of Various Disposable Acupuncture Needles Used in South Korea, Journal of Pharmacopuncture (2022)

4. Thermal conduction: copper vs stainless steel

Copper has a thermal conductivity 20 to 25 times higher than that of stainless steel, close to that of silver.

This property promotes rapid heat transmission along the needle. A study on heat transfer confirms that highly conductive materials improve heat diffusion.

Source: Evaluation of Heat Transfer in Acupuncture Needles (2015)

A clinical study on silver needles (2019) shows superior efficacy in warm needling. Copper, whose conductivity is close, could present similar properties, although this has not been formally demonstrated.

Source: Silver-needle warm acupuncture efficacy (2019)

In practice, high conductivity promotes faster heat transfer to the tissues. The clinical effect, however, depends on multiple factors: type of moxa, combustion, distance to the skin and duration of exposure.

5. Observed temperatures and thermal effect

The high temperatures observed at the handle and junction confirm the material's exposure to significant thermal stresses.

Data for copper are not detailed in available studies for these zones. However, measurements at skin contact suggest more effective thermal transmission.

It is important to note that the perceived temperature and clinical effect also depend on other factors: type of moxa, combustion, distance to the skin and duration of exposure.

6. Length and needle selection

A distance of approximately 3.5 cm between the moxa and the skin offers a good compromise between thermal efficacy and safety.

• Superficial insertion (0.5 to 1 cm): 25 mm needles
• Deeper insertion: 40 mm needles (recommended)

Diameter plays a more mechanical than thermal role:

• Minimum: 0.25 mm
• Ideal: 0.30 mm for better stability

Source: Safety of different distances in warm-needling moxibustion

7. Safety precautions

The handle can reach 300 to 400°C, and a moxa cone typically burns for 5 to 12 minutes.

• Wait for the moxa to be completely extinguished before removal (it may remain incandescent)
• Use a moxa spatula, never fingers
• Monitor the area continuously throughout the entire stimulation

8. Purchasing and traceability

Needles are predominantly manufactured in Asia but must comply with European standards (class IIa medical devices).

It is recommended to favour a European supplier to guarantee:

• Traceability and regulatory compliance
• Liability in the event of a problem
• Transparency regarding composition

Labels to check for:

• Silicone-free
• Uncoated
• No coating

The absence of clear information (notably on certain marketplaces) should be regarded as a warning signal.

Conclusion

• Silicone-free needles: fewer residues in the body, and no manufacturing defects masked by the coating
• Copper handle for efficient thermal conduction
• Length adapted to insertion depth
• Diameter ≥ 0.25 mm for moxa stability

The choice of equipment directly influences the safety and quality of thermal stimulation. Rigorous selection, based on technical criteria and scientific data, is essential in practice.

Scientific sources

• The Biological Safety of Stainless Steel Needles Used in Warm-Needling (2010)
• On the Hazard Caused by the Heat of Acupuncture Needles (2013)
• Evaluation of Heat Transfer in Acupuncture Needles (2015)
• Silver-needle warm acupuncture efficacy (2019)
• Periorbital Silicone Granulomatosis (2020)
• Silicone Biomaterials (2004)
• Safety of different distances in warm-needling moxibustion
• Morphological and Chemical Analysis of Various Disposable Acupuncture Needles Used in South Korea (2022)