With the progress of the application of photoacoustic electrotherapy in clinical medicine, more of the above energy-based devices are used to treat skin and mucosal diseases or improve appearance. These devices, whether thermal or non-thermal, will produce varying degrees of inflammatory response to the skin and mucosa. Most of them can be repaired by themselves, and a few may leave long-term adverse reactions or even complications if they are not handled properly. From the perspective of evidence-based medicine, this article analyzes and summarizes the postoperative repair strategies of energy-based photoacoustic electrotherapy.

1. Basic principles and overview of photoacoustic electrotherapy

Photoacoustic electrotherapy is a physical therapy method that has gradually developed on the basis of the medical application of laser and intense pulsed light technology. Early phototherapy developed into laser technology in the 1960s, and then developed into intense pulsed light (IPL). It was then further promoted to the application of radio frequency and focused ultrasound technology in clinical treatment and medical cosmetology. Therefore, the American Society of Laser Medicine specifically defined the term "energy-based device". Its principles mainly include: selective photothermal action principle, selective photothermal decomposition principle, photodynamic therapy principle and laser light knife tissue cutting, gasification and fractional laser treatment principle, weak laser and weak light light regulation mechanism.

Directly using focused high-energy laser as a light knife to perform surgical excision treatment, mainly laser mole removal, cyst removal, benign and malignant superficial tumor excision, gingival shaping, frenulum shaping and scar excision.

Fractal laser is a technology that uses array-arranged tiny laser beam output to perform exfoliation and non-exfoliation treatment on target tissues, such as fractional CO2 laser treatment of scars.

In recent years, focused ultrasound has been used to selectively heat target tissues such as collagen or fat in the skin to achieve the purpose of skin rejuvenation. There is also a wrinkle removal and skin rejuvenation treatment that uses radio frequency technology (monopolar and bipolar radio frequency) to heat collagen in the skin.

2. Skin and mucous membrane reactions after photoacoustic electrotherapy

2.1 Adverse reactions after photoacoustic electrotherapy

2.1.1 Erythema, edema and capillary dilation

Local erythema after laser surgery often occurs within 24 hours after laser surgery, sometimes accompanied by wheals or local edema. Erythema or edema after laser treatment around the eyes and mouth may last slightly longer, up to about 48 hours. Persistent vasodilation often occurs after laser skin resurfacing.

2.1.2 Dryness, desquamation, itching and skin sensitivity 

After laser surgery, especially after excessive exposure to high-energy intense pulsed light or ablative laser treatment, dry skin, desquamation, itching, discomfort and even sensitive skin often occur. Timely facial hydration treatment, selection of functional moisturizing repair cream for skin care, and local sun protection can reduce the above adverse reactions and reduce the occurrence of sensitive skin.

2.1.3 Purpura 

Purpura often occurs after pulse dye laser surgery, especially after laser treatment with a pulse width shorter than 6ms. It often lasts for 5 to 7 days, then gradually fades until it disappears. Purpura is more common in people with darker skin on the lower limbs. The duration of purpura can be shortened by using long pulse width, low frequency, appropriate cooling and light-shielding agents.

2.1.4 Erythema, edema, exudation and scab around hair follicles 

Erythema and edema are common after laser hair removal, and generally disappear gradually after a few hours; exudation and scab are common after invasive laser treatment, such as laser peeling, Q-switched laser treatment, etc., and generally disappear in 3 to 10 days.

2.1.5 Pain 

Pain is a common adverse reaction during and after the operation of energy-based equipment. There are individual differences in the degree of pain, and different equipment, parts, ages, and technical operations are related to pain to a certain extent. The main methods to relieve pain are cooling the treatment area and using local anesthetics. There are three main cooling methods: direct use of solid contact cooling devices, automatic refrigerant spray or cold spray. Cooling can cool the skin of the treatment area, relieve pain, reduce edema and reduce the harm of residual thermal burns.

2.1.6 Burns 

Burns are a common complication of photoelectric therapy. The reactions and consequences of burns include erythema, blisters, erosions and scars. The main reasons are too high energy, too short pulse width, or insufficient epidermal cooling. Safe parameter settings, appropriate epidermal cooling methods and careful selection of continuous pulse lasers can effectively avoid burns. Erythema lasts for 24 to 72 hours and can disappear naturally without special treatment. Erythema caused by non-ablative lasers lasts for a shorter time, while the incidence of erythema caused by ablative lasers is higher and can last for weeks to months. When blisters or erosions occur, the wound surface should be treated in time. Wound protection and prevention of infection are also the key to reducing scar formation.

2.1.7 Other rare or uncommon adverse reactions 

Other rare or uncommon adverse reactions such as local skin nodules and cutaneous nerve damage after laser surgery can be treated by specialists.

2.2 Complications after photoacoustic electrocosmetic surgery

2.2.1 Hypertrophic scars

The appearance of hypertrophic scars indicates severe photoelectric damage, which is caused by damage to the dermal collagen fibers and skin appendage structures, and there may be a family susceptibility. It is often caused by excessive energy, inappropriate cooling methods, postoperative infection, pulse overlap at the purpura, excessive repeated treatment and inappropriate treatment.

2.2.2 Depressed scars

Depressed scars are relatively rare and are often caused by excessive energy. Excessive energy and inappropriate cooling damage the dermal collagen fibers and subcutaneous fat tissue, leading to atrophy of the subcutaneous tissue. Depressed scars rarely improve over time and usually need to be repaired by injection filling or other treatment methods.

2.2.3 Hyperpigmentation (PIH) PIH is common in dark skin types, with an incidence of nearly 20% in patients treated with IPL and up to 45% in type IV skin. DPL and KTP lasers are also more likely to produce pigmentation, and ablative COz lasers are more likely to produce PIH. PIH can also occur after Q-switched laser and pulsed dye laser treatment. Proper parameter settings and operating techniques are crucial to preventing PIH.

2.2.4 Hypopigmentation and depigmentation
Hypopigmentation and depigmentation are less common and often occur after treatments such as Q-switched laser and pulsed dye laser. The hypopigmentation caused by Q-switched laser can be temporary or permanent. When treating port wine stains with pulsed dye laser, the probability of hypopigmentation is about 2%~31%. A relatively long pulse duration can be selected, and the energy should not be too high to reduce the occurrence of hypopigmentation. Improper use of energy during hair removal can also cause depigmentation, especially in people with dark skin.

2.2.5 Hair loss
Hair loss is less common and can be seen with Q-switched lasers, especially when the eyebrow is washed multiple times with Q-switched lasers. It can also occur during long-pulse 1064nm laser treatment. For example, when long-pulse 1064nm laser is used to treat hemangiomas in the eyebrow area, it may cause eyebrow hair loss. This is caused by the thermal effect of the laser penetrating deeper, which damages the hair papilla at the root of the hair follicle.
2.2.6 Acne fulminans
Acne fulminans can occur in patients treated with skin resurfacing lasers or intense pulsed light therapy, with an incidence of 3% to 15%; when photodynamic therapy is used to treat acne, the original acne lesions often worsen. This type of acne fulminans has a good prognosis and most of them can heal on their own.
2.2.7 Abnormal deepening of tattoo pigment and tattoo granuloma

Some tattooed people may experience dermatitis and allergies after phototherapy, which is caused by changes in tattoo pigments leading to allergic reactions, which can cause the original tattoo color to deepen or granulomas to form.

2.2.8 Infection
Infection is uncommon and can be bacterial, fungal and viral. Bacterial infection is often caused by Staphylococcus aureus and is common after ablative phototherapy with exudation, blisters and scabs. It usually occurs 4 to 7 days after surgery and needs to be treated in time. Viral infection often occurs after laser skin resurfacing, with an incidence rate of 1%. It is common after phototherapy around the mouth, and there are reports of disseminated HSV infection and severe scar formation. Fungal infection is rare and has been reported after ablative phototherapy, manifested as local erythema and itching.

3. Skin and mucosal repair after photoacoustic electrotherapy

Repair in medicine refers to the restoration of the structure and function of the damaged parts by the body after tissue and cell damage, which is mainly achieved through cell regeneration. Nowadays, people are no longer satisfied with simple covering up for beauty and skin care, and they require "smile repair" for the treatment of problematic skin.

The physiological repair of the body is a basic repair, which needs to go through the following stages: hemostasis and inflammatory response period, epidermal regeneration period, granulation tissue formation period, fiber and matrix formation period, wound contraction period, angiogenesis period, and matrix and collagen remodeling period8. With the widespread application of photoacoustic electrotherapy technology, various types of repair materials continue to appear, which play a repair and maintenance effect on the skin after laser or photoelectric surgery. Commonly used skin barrier repair materials include: chitosan, hyaluronic acid, cell growth factor and collagen, etc.
3.1 Basic care
In the process of skin and mucous membrane repair, various local and systemic factors affect the wound healing process by affecting one or several pathophysiological processes of wound repair. Local factors include foreign bodies, infection, proper oxygen content, local blood supply, etc.; systemic factors include age, sex hormones, stress state, diabetes, etc. In addition, obesity, smoking, alcoholism, nutritional factors, etc. Whether it is ablative or non-ablative photoacoustic electrotherapy, proper basic care is necessary.

3.1.1 Moisturizing Photoacoustic electrotherapy can damage the skin's barrier function and increase the patient's discomfort. Mask materials containing ceramide-inducing hyaluronic acid and collagen can be used to moisturize and repair the barrier function.

3.1.2 Sun protection
In the short term after surgery, wear a sun hat, long-sleeved tops and long pants, and use an umbrella to block UV rays, etc., to avoid prolonged exposure to sunlight. Use sunscreens with high safety and good sun protection effects. The recommended sunscreen index (SPF) is above 30, PA (+++).

3.1.3 Diet
After photoacoustic electrotherapy, you should pay attention to a light diet. Avoid eating photosensitive foods such as celery, gray vegetables, rapeseed and mustard, as well as spicy foods before healing. Eat more foods rich in vitamin C and vitamin A. Some drugs such as tetracyclines and quinolones also have certain photosensitivity. Appropriate supplementation of essential nutrients such as protein, fat and sugar, and drinking more water can promote the repair of skin and mucous membranes.
3.1.4 Others
Appropriately elevating the treated area after treatment can reduce the edema reaction of the tissue; avoid scratching the skin of the treated area during the period from surgery to healing; avoid swimming or strenuous sports activities, etc. 3.2 Repair of non-ablative treatment Compared with ablative treatment, non-ablative treatment has a shorter recovery period and fewer and milder adverse reactions. 3.2.1 Cold spray and wet compress
Cold spray or towel-wrapped ice cubes can be used to cool the treated area. When using ice cubes, avoid making the skin temperature too low. Avoid rubbing the skin. If erythema, swelling, and exudation are obvious, pure water, saline, or 3% boric acid solution can be used for cold wet compresses.
3.2.2 Prevention of infection
It is necessary to prevent postoperative skin infection. If necessary, topical antibiotic preparations such as mupirocin can be applied thinly to the wound surface. For patients with a history of herpes simplex in the treatment area, oral valacyclovir and/or topical acyclovir ointment can be used to prevent viral infection.
3.2.3 Promoting healing
Currently, various repair materials are used in clinical practice. After surgery, fibroblast growth factor (FGF), epidermal growth factor (EGF) or other growth factors that promote wound healing can be sprayed externally to accelerate wound healing. In addition, many studies have shown that the use of medical cold patches and plant hydrogel cold patches after laser surgery have positive effects in anti-inflammation, anti-infection, hemostasis, astringency and accelerated wound healing.

3.3 Repair of ablative therapy

Repair of ablative therapy is a complex process, including inflammatory response, cell proliferation, matrix deposition and tissue remodeling, with the participation of multiple cells and cytokines. Expected complications include persistent erythema, pigment changes and even infection and scarring. In order to minimize the occurrence of postoperative complications and obtain the best treatment effect, it is particularly important to promote skin regeneration and repair after ablative therapy.

The principle of postoperative wound care is to prevent infection, promote healing and avoid scar formation. Guide patients to develop good skin care habits and effective postoperative care. Generally, the wound surface should be kept clean after the treatment is completed. Do not apply oily skin care products, sunscreen, etc. to the wound area. Try to use less or no makeup to reduce the occurrence of contact dermatitis and infection.

After exfoliative treatment, the skin tissue usually swells and exudates. Cold compresses can be applied according to the immediate skin performance, generally for 15 to 30 minutes, and care should be taken to avoid frostbite. If swelling and exudate are obvious, 3% boric acid solution can be used for wet compresses.

Postoperative wound care mainly includes two methods: open or closed wounds. Studies have found that there is no significant difference in the results of the two treatment methods. The specific use should be determined according to the size, location, depth of surgery, and the patient's work, lifestyle, and economic status of the wound. Within two or three days after treatment, the wound can be closed with a dressing. The dressing can be removed after the exudate is reduced, and antibiotics can be used on the wound. Current research and clinical practice have confirmed that wet wounds heal faster. Continuous application of Vaseline ointment containing antibiotics can prevent infection, prevent the formation of hard scabs on the wound surface, and promote wound healing. At this stage, the combined use of growth factors can promote the formation of granulation tissue, accelerate the process of wound re-epithelialization, and reduce scarring. Epidermal growth factor and platelet growth factor are often used clinically to prevent scarring. About four or five days after treatment, thin scabs will form on the wound surface of most patients, and the thin scabs will gradually fall off in about 7 to 10 days. After that, patients should be guided to use appropriate medical skin care products to promote the recovery of skin barrier function. Moisturizing and sun protection are necessary within half a year after wound healing. Keeping the skin moist is beneficial to skin metabolism and tissue regeneration.
Scarring is the most serious and rare complication after ablative treatment. Congenital factors, a history of oral retinoic acid drugs before surgery, too deep treatment, infection, and improper postoperative care will increase the risk of scarring. Proper postoperative care and accelerated wound healing can reduce the risk of scarring. If local redness and thickening of the skin occur, the possibility of scarring should be considered. Local closure with glucocorticoid drugs or dye laser treatment can be performed.

The skin is extremely fragile after photoacoustic electrotherapy and needs careful care to promote repair and reduce adverse reactions. At this time, the cold air therapy device outputs low-temperature airflow to relieve inflammation and discomfort in a short time; the medical dressing contains active ingredients, which can deeply moisturize, repair the barrier, and significantly promote wound healing. Patients are advised to pay attention to and use these two types of products reasonably after photoacoustic electrotherapy to provide strong support for skin repair and regeneration, protect skin health, and bloom beauty.

Foremed Legend

The core founding team of Suzhou Foremed Legend Medical Technology Co., Ltd. comes from well-known universities at home and abroad such as Peking University. Foremed Legend focuses on the design, research and development and application of high-end medical beauty optoelectronic equipment based on compliance and product strength. It is committed to becoming a leading company in the field of global high-end medical beauty optoelectronic equipment, a provider of integrated diagnosis and treatment intelligent solutions, and a pioneer of medical beauty data integration platform.

Through the development of a series of underlying key technologies, Foremed Legend has independently developed a number of high-end medical devices, including picosecond laser therapy devices, long pulse laser therapy devices, intense pulsed light therapy devices, photoacoustic imaging skin detection devices, and cold air therapy devices. It continues to deepen the research and development of core product technologies, using better technical solutions to benefit the vast number of beauty seekers.  

Adhering to the principle of technology for good, Foremed Legend will work with industry and ecological partners to bring more safe and effective medical beauty optoelectronic equipment and integrated diagnosis and treatment solutions to the global medical beauty market.