Traditional Chinese medicine paraffin therapy: an evidence-based overview from a modern medicine perspective

External therapy of traditional Chinese medicine and paraffin therapy are both traditional Chinese forms of treatment. In recent years, external use of traditional Chinese medicine combined with paraffin therapy, which involves combining meridians, acupoints, drugs, and hyperthermia, has demonstrated great effectiveness in treating certain conditions. An overview of traditional Chinese medicine paraffin therapy (TCMPT) is provided by this article. Additionally, this article describes a new classification of TCMPT, mechanism of action, clinical treatment, indications contraindications and adverse events reports.


Introduction and brief history
In recent years, 'traditional Chinese medicine non-oral drug therapy' (TCMNDT) received widespread attention because of its wide range of adaptive treatment, targeted therapy that can quickly and effectively alleviate the patient' s pain and other advantages [1]. The proportion of TCMNDT in treatment has been included in the Healthy China 2021-2022 Assessment Program [2]. At the same time, the state will lead the development of 'National Standards For the Industry of TCMNDT' , systematize and promote the promotion of TCMNDT.
External therapy of traditional Chinese medicine refers to using non-oral medicine to stimulate meridians, acupuncture points, skin, mucous membranes, muscles, tendons, and bones to prevent and cure diseases [3]. Modern medical research has shown that the external therapy of traditional Chinese medicine improves blood circulation, promotes the absorption and mechanization of hematoma, regulates the endocrine system, etc. Drugs penetrate the subcutaneous tissue through the skin in the affected area, and produce the relative advantage of drug concentration in the local area, reduce the local inflammatory response, promote local tissue fluid circulation, and achieve the purpose of improving symptoms [4]. The most common external therapies of traditional Chinese medicine include herbal fumigation, acupoint application, acupuncture, massage, etc [5]. Herbal acupoint application is one external therapy with Chinese characteristics, in which herbal paste is applied externally to acupoints. As a result of its practical convenience and fewer side effects, the therapy is suitable for wide application in the community [6].
Paraffin therapy has a long history in China and is performed by melting and heating medical paraffin and applying it to the surface of the body [7]. 'Compendium of Materia Medica' has recorded that foot frostbite applies thick fried yellow paraffin. Qi Kun, a surgical expert in the Qing Dynasty, comprehensively described the operation methods and indications of paraffin therapy in 'Surgical Achievement' [8]. Because of its high thermal capacity, low thermal conductivity, and long cooling time, paraffin wax is a good medium for hyperthermia conduction when in close contact with the body [9]. Paraffin therapy is a real natural therapy free of trauma, pain, and side effects. This method is simple, feasible, and inexpensive, making it among the most effective and worthy of promotion rehabilitation methods [10].
Recently, traditional Chinese medicine paraffin therapy (TCMPT) has emerged, which was based on ancient paraffin therapy, combined the mechanisms of action of various types of treatment such as meridians, acupoints, drugs, and hyperthermia from a modern medical perspective, so that it has curative properties that cannot be achieved through simple drugs, paraffin therapy, or acupuncture therapy alone [11]. Other reviews on TCMPT only review its treatment of different diseases, whereas this reviews the types of TCMPT, mechanism of action, clinical treatment, indications contraindications, and adverse events reports, to provide new ideas for the development of TCMPT based on traditional paraffin therapy and to promote the better application of traditional Chinese medicine in clinical treatment.

Mechanisms of action and reported effects of TCMPT
The mechanism of action in external therapy of traditional Chinese medicine is mainly twofold. On the one hand, external therapy of traditional Chinese medicine promotes local blood circulation, improves immune function, and prevents and treats diseases by stimulating body surface skin (including acupoints); On the other hand, this therapy, through the transdermal drug delivery system, avoids the first-pass effect of the liver, prevents drug inactivation caused by digestive enzymes and hepatic drug enzymes, increases the body's blood concentration and evades toxic side effects of drugs on the liver and gastrointestinal tract. Therefore, the acupuncture point application method both stimulates the acupuncture point and plays an obvious pharmacological effect which has a dual therapeutic effect [12]. Xie et al. suggested that drugs acting on acupoints produce specific thermal changes making some components of drugs easier to penetrate the skin and reach deep acupoints [13]. Zhang et al. believe that herbal acupoint application in modern pharmaceutics called percutaneous drug delivery system avoids oral administration may occur liver first-pass effect and gastrointestinal inactivation improve the effective blood concentration [14].
One of the mechanisms of action of paraffin therapy is that it significantly increases microcirculation expands local capillaries and accelerates blood circulation abates tissue edema and excludes pain-causing substances allowing inflammatory infiltration and absorption to achieve the purpose of detumescence and pain relief. At the same time wax has oily components scar tendon contracture which can promote its softening and release and restore elasticity. In addition, paraffin gradually reduces its volume during cooling, and shows mechanical compression, which can prevent tissue lymph and blood exudation and enhance the absorption of exudation [10]. Wang et al. theorized that mineral oil contained in paraffin possessed a certain chemical effect on the body such as stimulating the growth of epithelial tissue and preventing bacterial reproduction which contributed to the healing of superficial skin wounds11 (Fig. 1).

Classification of TCMPT types
Based on the relevant literature and clinical practice, this article suggests that TCMPT may be divided into five categories:

Paraffin therapy combined with external application of herbal paste
Paraffin therapy combined with external application of herbal paste involves grinding the herb into powder, forming it into pellets with freshly squeezed ginger, maltose, or vaseline ointment, applying them to selected body parts, after heating the medical paraffin to 45-50 ℃, pouring it into a plastic bag, and then placing it on the treatment site [15, 17, 18, 23, 24, 29-31, 33, 37-39]. If the selected body parts are acupoints, it can also be called herbal acupoint application combined with paraffin therapy [20,28].

Paraffin therapy combined with Chinese herbal iontophoresis
Applying paraffin therapy combined with Chinese herbal iontophoresis involves the following steps: Applying paraffin therapy combined with Chinese herbal iontophoresis involves the following steps: pouring the concentrated decoction of the Chinese medicine solution onto the introduction pad using an introduction instrument and placing it on the treatment area at a temperature of 40-45 ℃. After the Chinese herbal iontophoresis, heat the paraffin block to 45-50 ℃ and then place it on this treatment site. The treatment sites of some studies are acupoints [16,25].

Chinese herbal paraffin block therapy
Putting the medical paraffin with a melting point of 50-55 ℃ into the paraffin box and adding the powdered Chinese herbal to dissolve it completely, then spread the dissolved Chinese herbal paraffin on a tarpaulin to make Chinese herbal paraffin block with a thickness of 2.0-3.0 cm, and then applying to the treatment site [19]. Some studies will use acupuncture, Chinese herbal fumigation, or other treatment after Chinese herbal paraffin block therapy [22,27,32].

Paraffin therapy combined with Chinese herbal package
Soaking a gauze package in Chinese herbal decoction heated to 45-55 ℃ for 10-20 min. Then place the Chinese herbal package on the treatment site, put a paraffin wax cake on it and wrap it with a cotton pad [21,26,35,36].

Paraffin therapy combined with Chinese herbal collapse therapy
Putting the Chinese herbal into a non-woven bag, soaking it in warm water for 30 min, placing it in an electric constant temperature drying water tank, adjusting it to 80 ℃ for heating, and then applying it to the treatment site after the temperature has dropped to (40 ± 2) °C. After heating the medical paraffin to 45-50 ℃, place it on the treatment site [34].

Indications
TCMPT has been used for years to prevent and treat diseases. It is beneficial for many diseases, among which internal medicine diseases include digestive system diseases (chronic gastritis [15,16], epigastric pain [17,18]), nervous system diseases (high levels of muscle tension of limbs in children with spastic cerebral palsy [19], diabetes peripheral neuropathy [20]). In the treatment of chronic gastritis in digestive system diseases, Chen et al. [15], based on routine nursing methods, applied the self-made TCM 'Kunning ointment' to the stomach and epigastric region once a day for more than 6 h. At the same time, the heated medical paraffin was placed in a 15 cm×20 cm sealing bag at a temperature of 50 ℃ and coated on the 'Kunning Ointment' and retained for 30 min. The results showed that herbal acupoint application combined with paraffin therapy in the treatment of chronic gastritis was significant. Wang et al. [16]used electric kerotherapy combined with Chinese herbal iontophoresis based on the control group. The electric kerotherapy acupoints were Zhongwan (CV12), Shenque (CV8), and Guanyuan (CV4), 30 min each time. The acupoints selected for Chinese herbal iontophoresis were Weishu (BL21) and Dachangshu (BL25). Methods: The concentrated decoction was evenly poured on the import pad by the imported instrument, and the temperature was 40-45 ℃. The results showed that electric kerotherapy combined with Chinese herbal iontophoresis in the treatment of chronic gastritis was remarkable, which could improve the clinical symptoms of gastric distension, gastric pain, abdominal distension, loss of appetite, and belching (Table 1).
In the treatment of epigastric pain in digestive system diseases, Huang et al. [17] on the basis of the control group treatment, applied a block of selfmade 'warming stomach prescription' to the stomach and epigastric region. Then the medical paraffin was heated to 45-50 ℃, poured into the plastic bag, and placed on the TCM block for external application, 30 min each time. The results showed that herbal acupoint application combined with paraffin therapy is a   simple, effective, safe, simple and easy-to-use treatment method with no obvious adverse effects, and is worthy of clinical promotion. You et al. [18] on the basis of the control group treatment, applied the TCM 'pain-relieving ointment' to the stomach and epigastric region. Then the medical paraffin was heated to 45-50 ℃, poured into the plastic bag, coated on the 'pain-relieving ointment' and covered with a small blanket to keep the area warm. The results showed that herbal acupoint application combined with paraffin therapy can effectively relieve the discomfort symptoms of patients with gastric pain. Surgical diseases include chronic soft tissue injury disease (supraspinatus tendinitis [21], scapulohumeral periarthritis [22][23][24]), bone and joint diseases(knee osteoarthritis [25][26][27][28], rheumatoid arthritis [29][30][31], ankylosing spondylitis [32], cervical spondylopathy [33,34], lumbar disc herniation [35,36]), and orthopedic diseases(thoracolumbar compression fracture [37], distal radius fracture [38], patellar fracture [39]).

Age of patients using TCMPT
According to the included literature, except for the literature on children's diseases, most of the patients included in the literature are 18-75 years old, and some special diseases (such as thoracolumbar compression fracture) will increase the age to more than 80 years old; among them, patients with rheumatoid arthritis, knee osteoarthritis and lumbar disc herniation who received TCMPT were mostly over 40 years old. It can be seen that TCMPT is suitable for people of all ages, but for people under 18 years old and over 75 years old, it is necessary to pay attention to the types of diseases used in TCMPT ( Table 2).

Contraindications
TCMPT is contraindicated directly on skin inflammation, any skin lesion, eyes, lymph nodes, or varicose veins. Patients with cancer, as well as those with serious diseases of the heart, liver, brain, kidney, etc., are contraindicated [40,41]. It is also contraindicated in patients who have pacemakers or suffer from hemophilia. An acute infection, the use of anticoagulants, bleeding disorders, severe heart conditions and pacemakers, pregnancy, puerperium, menstruation, anemia, medical problems, allergic reactions to topical medications, and hypersensitive skin are all contraindications to TCMPT [15,42].

Adverse events
TCMPT is a form of combination therapy. The following adverse events (AEs) have been reported with this therapy: In general, external therapy of traditional Chinese medicine is relatively safe and AEs are relatively rare. Majority of AEs are mild or moderate in severity [43]. The most common AEs to herbal acupoint application are skin redness, itchiness, tingling, congestion, rash, etc [44][45][46].An important factor is that the patient's skin is allergic to the herb or tape. Blisters and ulcers may form if the treatment is applied too long. Li et al. [47] reported a case of paraffining burns, in which the patient's right knee was burned owing to the lack of awareness of the health provider. Wang et al. [47] found that treatment groups that used paraffin therapy had arisen skin diseases (skin allergies), but did not have vomiting, scalds, respiratory failures, heart failures, or deaths. This article summarized the treatment-related adverse events that occurred during the trial [47] (Table 3).

Infection control measures
Many articles mentioned that the most common adverse reaction caused by paraffin therapy burns. To reduce the occurrence of burns, paraffin should be cooled to the appropriate temperature before treating the patient, the patient should be asked how he/she feels at any time during the treatment process and the patient's skin should be observed, if erythema, blisters, scratching, etc. should be stopped immediately; cold water should be avoided after the treatment [20]. If the burn wound has purulent secretions, the wound needs to be cleaned and the infection controlled by thoroughly flushing the wound with 3% hydrogen peroxide solution, then rinsing the wound with 0.9% saline and applying topical burn ointment locally; if the wound has blisters, small blisters with iodophor disinfection, saline rinse, topical burn ointment; large blisters washed with saline, iodop hor disinfection, with 5 ml sterile syringe to extract the blister liquid, topical burn ointment [48].

Summary
In conclusion, TCMPT, which combines meridians and acupoints, drugs, and hyperthermia, has been very effective in some diseases. We reviewed a new classification of TCMPT, mechanism of action, clinical treatment, indications contraindications and adverse events reports to provide new ideas for the development of TCMPT based on traditional paraffin therapy and to promote the better application of traditional Chinese medicine in clinical treatment. This article suggested that TCMPT can promotes local blood circulation, improves immune function, relaxes joint ligaments, muscles and tendons, evades toxic side effects of drugs on the liver and gastrointestinal tract, excludes pain-causing substances allowing inflammatory infiltration and absorption, and prevent tissue lymph and blood exudation but also to enhance the absorption of exudate, and loosens tendon contractures, restores elasticity; it is divided into five categories, namely paraffin therapy combined with external application of herbal paste, paraffin therapy combined with Chinese herbal iontophroesis, Chinese herbal paraffin block therapy, paraffin therapy combined with Chinese herbal package, paraffin therapy combined with Chinese herbal collapse therapy. The most common AEs to TCMPT are skin diseases (including skin redness, itchiness, tingling, congestion, rash). It can be seen from the included literatures that TCMPT can be used to treat digestive system diseases, nervous system diseases, chronic soft tissue injury disease, bone and joint diseases, and orthopedic diseases. But these literatures are all Chinese, and most of them are not of high quality. Therefore, attention should be paid to improve the quality of literature in future related trials (including clarifying blinding and adding descriptions related to adverse effects, etc.). If we want to vigorously promote TCMPT, the types of paraffin, the treatment sites for different diseases, and the size of ointments made of Chinese herbs need to be  standardized. At the same time, TCMPT as part of Chinese medicine treatment, personalized treatment is also one of its characteristics, for example, the choice of type and dosage of Chinese herbs, differences in individual treatment sites, frequency of treatment, etc., all require us to develop specific treatment protocols according to the patient's situation. Also, TCMPT is still mainly used for the treatment of surgical diseases, and it is not widely used in clinical diseases, and few people understand and apply it. Therefore, we need to promote TCMPT more recently and apply it to more kinds of diseases, so as to provide new treatment methods for different diseases.