*4.1.2 Pros and cons*

*Depigmentation*

achieved [17].

*3.3.3 Side effects*

the skin!

**4.1 Cryotherapy**

*4.1.1 Procedure*

**4. Physical therapies for depigmentation**

contact dermatitis or any side effects due to the same.

of koebnerization, cryotherapy is more effective.

*3.3.2 Administration of treatment*

The area to be treated is cleaned with spirit/alcohol. Application of phenol is done with the help of a swab soaked with phenol until cutaneous frosting occurs. There might be a burning sensation experienced by the patient for approximately 60 seconds, which gradually decreases in intensity but can last from minutes to hours. In a case study reported by Zanini and Machado Filho, they reported the use of 88% phenol on a 62-year-old female patient. Post 2 sessions, with a gap of 45 days, total elimination of residual pigmentation was

In general, 88% phenol does not produce any major complications when used in limited areas. However, some complications such as cardiotoxicity and other systemic toxicities have been reported in patients treated with medium and deep peeling over larger areas. Its cellular uptake is both rapid and passive because of its lipophilic character and signs of systemic toxicity develop soon after exposure. Cardiovascular shock, cardiac arrhythmias, and bradycardia, as well as metabolic acidosis, have been reported within 6 hours of skin-peeling procedures with phenol [17]. Other complications include non-esthetic scar formation, dyschromia, and development of herpetic eczema. However, the authors of this chapter have also noted a paradoxical response, wherein phenol application led to repigmentation of

Depigmentation with topicals is effective; however, they come with their share of side effects and can take up to 10 months or more for completion of the process and rarely complete depigmentation may not be achieved. Depigmentation by physical means, i.e., by cryotherapy and lasers, can be done when rapid depigmentation is desired or when patients have not responded well to topicals or have had

Cryotherapy is nothing but cold therapy or the use of low temperatures to treat

Initially, spot testing by a single freeze-thaw cycle is done. Once the edema and erythema subside, patches are treated with cryotherapy 3–6 weeks later. Either CO2 or liquid N2 can be used. A 2-cm flat-topped and round cryoprobe is used at approximately 40 mm from the skin surface. The whole patch is frozen with a single freeze-thaw cycle from the periphery followed by forming successive rows inward.

a variety of tissue lesions. With cryotherapy, it is possible to achieve rapid and permanent depigmentation via irreversible tissue damage resulting from intracellular ice formation. Liquid nitrogen is used as a cryogen for clinical use. The degree of damage depends on the rate of cooling and minimum temperature achieved. Further, inflammation develops within 24 hours of the treatment, which contributes to destruction of lesions via immunologically mediated mechanisms. In areas

**60**


### **4.2 Laser therapy**

Another faster method of depigmentation is the use of laser therapy. Lasers have been advocated more than MBEH and other bleaching agents due to their failure rate, as they have been proven to selectively destruct the melanocytes causing depigmentation. Further the risk of scar formation is minimized with laser therapies [16].

Mainly, the Q-switched ruby (QSR, 694 nm) and alexandrite (755 nm) lasers have been used in depigmentation. Both of these lasers operate in a similar manner in terms of mechanism of action. They induce photothermolysis of the pigmented lesions as they have wavelengths between 600 and 800 nm. These wavelengths are more readily and well absorbed by melanin. The frequency and pulse width is adjusted according to the skin type of the patient by a trained and experienced dermatologist. A maximum of 80 cm2 area is treated per session.


#### *Depigmentation*

Some other potential Q-switched lasers that can selectively destruct melanocytes include neodymium:yttrium aluminum garnet (Nd:YAG) laser (1064 nm) and the frequency-doubled Q-switched Nd:YAG laser (532 nm) [1]. In a study by Boen et al., Q-switched ruby laser (QSRL) 694 nm, Q-switched alexandrite laser (QSAL) 755 nm, and picosecond 755-nm alexandrite lasers provided the most significant pigment reduction when different recalcitrant pigmented areas of the body were treated by the abovementioned lasers over different areas in the same patient. In all the patients treated with this laser therapy, no adverse reactions apart from mild postprocedure erythema and crusting were noticed. The picosecond laser poses more advantages over the traditional Q-switch laser as it has increased photochemical action due to shorter pulse duration, requires lesser treatment sessions, and has reduced specific photothermal damage. This results in an increase in the safety profile of the laser and improves the effectiveness of this therapeutic modality [19, 24–26].

### *4.2.1 Points to ponder*

