Cold-air skin cooling increases skin discoloration after laser treatment

Postinflammatory hyperpigmentation — discoloration that remains after skin inflammation has healed — is a common side effect in dark-skinned individuals after laser treatments. Dr. Woraphong Manuskiatti at Mahidol University in Bangkok, Thailand, and his colleagues examined whether adding cold-air cooling to laser treatments could reduce the incidence of this discoloration.

As reported in the September issue of the Archives of Dermatology, the researchers tested 23 Thai women with acquired bilateral nevus of Ota-like macules — a skin condition often found in middle-aged Asian women that involves spotlike blue-black or gray-brown patchy pigmentation.

The researchers treated the patients with a 1064-nm Q-switched Nd:YAG laser with an average fluence of 7 J/cm² over a 3-mm spot area on each side of the face. One side of each patient’s face was randomly assigned to laser treatment only, and the other received cooling during and 30 s before and after treatment.

The cooling device used ambient air to generate a permanent stream of cold air that reduced the skin temperature to between 4 and 5 ºC. Because cooling has been used in the past to protect the skin and reduce treatment-associated pain in a variety of laser procedures, the researchers were hopeful that it might reduce laser injury and, hence, minimize postinflammatory hyperpigmentation.

However, of the 21 patients who completed the study, 13 developed postinflammatory hyperpigmentation on the side of the face that received the cooling, while five developed the discoloration on the uncooled side.

To see whether the cold-air cooling was responsible for the discoloration by itself, the researchers tested two patients having the skin condition, who were not in the original study, with the cold-air technique alone — without laser treatment — on one side of each patient’s face. Neither patient developed postinflammatory hyperpigmentation.

The researchers believe that the unexpected findings are a result of pigment-producing cells and/or skin cells responding unfavorably to the combination of laser pulses and cold-air exposure. They recommend further research with other methods of skin cooling.