Craig G. Burkhart, MPH, MD
From the Medical University of Ohio
Medical University of Ohio
5600 Monroe Street
Sylvania, OH 43560
International Journal of Dermatology
Humans, together with all living organisms on the surface of the Earth, are exposed to wavelengths of energy across the entire electromagnetic spectrum, including radiowaves, microwaves, infrared, visible light, ultraviolet light, X-ray, and gamma rays. Such energy sources have both life-giving and life-endangering effects. For example, although ultraviolet light is essential for our well-being, in high doses it can also damage DNA, leading to the development of skin cancer. The interaction of radiation with matter depends on a number of factors, including power, spot size, duration of exposure, wavelength, and tissue properties.
For years, physicians have preached that overexposure to ultraviolet radiation is the main cause of skin aging and the
development of basal cell and squamous cell carcinomas. Ultraviolet light involves electromagnetic waves with wavelengths
in the range 290–400 nm. Interestingly, lasers and IPLs involve wavelengths in the optical spectrum (400–700 nm) and infrared spectrum (700–1000 nm). This form of electromagnetic energy penetrates deeper into the skin tissue, and is being proposed as an excellent treatment for photoaging and for skin rejuvenation. The only reported concerns to date have been the short-term minor side-effects of treatment pain, erythema, edema, hypopigmentation, hyperpigmentation, blistering, crusting, erosions, purpura, folliculitis, and reactivation of herpes. Despite the proximity of these treatment wavelengths to the professed feared wavelengths, any possible iatrogenic and deleterious chronic side-effects of this radiation remain mostly unknown and unexamined.
Theoretically, the new, more powerful lasers and IPLs may cause delayed deleterious side-effects. In short, photons of
electromagnetic energy are a highly energetic form of energy. Depending on the wavelength, laser energy will be transmitted
through skin layers and preferentially absorbed by a specific tissue chromophore, such as melanin, hemoglobin, nucleic
acids, amino acids, carotene, or urocanic acid in the skin.
The absorption of a photon of light by the skin initiates a photochemical reaction in the biomolecules and leads to a series of biological reactions.4 Absorption changes the distribution of electrons in the molecule and creates the singlet excited state. From this state, the molecule can emit fluorescence, lose energy as heat via internal conversion, undergo a photochemical reaction to form photoproducts, or change into a triplet excited state.
The technique for skin rejuvenation involves painting the treatment area with thousands of successive laser pulses. Recently, superpulsed lasers, which produce a peak power many times that of the same laser operating in continuous wave mode, have become popular. As the absorption spectra of oxyhemoglobin and melanin are not identical to the wavelengths of any specific laser, there is a tendency to compensate for lack of attraction to these target chromophores with power. Laser companies are not only making systems with more total energy, but are using this as a selling point.
One of the most worrisome areas in laser surgery is the theoretical risk of melanoma. Indeed, the wavelengths of most lasers and IPLs target dermal and follicular melanin, which is an important chromophore in the skin. Melanin serves as a radical scavenger and preserves the DNA from pyrimidine base formation. Melanocytes and melanin are part of our primordial immune system. The use of lasers leads to the production of various cytotoxic oxygen species, such as dihydroxyindole, within melanocytes, which can interact with DNA and act as nonspecific mutagens. Radical species, such as hydroxyl radicals, aqueous electrons, hydrogen radicals, superoxide anion, and hydrogen radicals, also induce DNA-strand breakage and base damage, and are mutagenic.
From studies with ultraviolet light, melanoma appears to be related to intense, intermittent exposures. The wavelength dependence of the induction of melanoma and alterations in cancer parameters, such as the tumor suppressor gene CDKN2A
and oncogenes N-ras and H-ras , have not been studied in the light of these higher energy sources of electromagnetic energy.
In short, there are concerns about the long-term safety of lasers and IPLs, including the possible risk of melanoma. Little work has been performed to assess cancer development with these particular wavelengths, despite the fact that the
manufacturers are continually adding extra power to their units. It should be noted that any association of skin cancer with lasers is purely an assumption, as there have been no reports of problems in the literature. Nonetheless, physician monitoring
for such potential problems appears to be warranted.