Special considerations for using PDT on skin of color

January 1, 2007

Choosing the right light source when treating skin of color can help avoid unwanted post-treatment hypo- and hyperpigmentation changes, and is key to a positive cosmetic outcome.

Las Vegas - Recent statistics show that there is a steady rise in the percentage of ethnic patients in the United States who undergo aesthetic therapies.

Therefore, dermatologists and aesthetic physicians are confronted with this rise and the challenges that go along with treating skin of color.

For example, when using photodynamic therapy (PDT), physicians must consider numerous influential factors. Choosing the right light source, finding optimal and safe treatment parameters, prepping the skin and post-treatment care are some of the crucial points that must be successfully dealt with to achieve optimal aesthetic results in cosmetic procedures, according to one specialist.

Dr. Bhatia says that the use of topical 20 percent aminolevulinic acid with photodynamic therapy (ALA-PDT) is on the rise for mild-to-moderate acne, and in photoaging and pigmentary disorders (off-label/not Food and Drug Administration [FDA] approved). Topical ALA-PDT is currently FDA approved only for the treatment of nonhyperkeratotic actinic keratoses of the face or scalp.

"PDT is a simple treatment utilizing a photosensitizing agent, light and oxygen to selectively kill cells via oxidative damage. For activation of the photosensitizer, the wavelength of the light must be in the absorption spectrum of the photosensitizer," Dr. Bhatia tells Dermatology Times.

Choosing right light

According to Dr. Bhatia, choosing the right light source when treating skin of color can help avoid unwanted post-treatment hypo- and hyperpigmentation changes, and is key to a positive cosmetic outcome.

He says that a continuous wave (CW) light source (broadband, red or blue) is a wise choice. Lasers or IPLs can be used, but longer wavelengths, longer pulse durations and lower energy settings are important here to avoid unwanted pigment destruction.

"Lasers at wavelengths with high absorption by melanin can be problematic at short pulse durations because of the photothermal effect on pigment. For better results, extended pulse durations should be used. Utilizing the same concept, the physician can deliver energy over even longer time periods with CW light sources, like blue or red light," Dr. Bhatia says.

It is known that some laser cooling systems may lead to pigmentary changes (cryogen-induced dyspigmentation). To avoid this problem, Dr. Bhatia uses lower cryogen settings or alternative cooling systems like the Zimmer cooler or contact cooling.

Pain is also occasionally an issue with CW light PDT. Dr. Bhatia suggests the use of an air cooling system like the Zimmer cooler to minimize the pain during a PDT procedure.

To minimize adverse effects when using PDT in darker skin types, Dr. Bhatia also advises reducing incubation times (short – one hour, or ultra-short – 30 minutes to 45 minutes contact). Shorter incubation times also help to avoid an excess PDT effect if the patient is exposed to excess ambient light post-treatment.

Prior to the PDT procedure, Dr. Bhatia likes to gently prep the skin with a mild peel or a microdermabrasion. Generally, he pre-treats the skin with a topical hydroquinone for two weeks to minimize post-treatment hyperpigmentation.

Follow-up procedure

Following a PDT treatment, Dr. Bhatia gently washes the face again and applies cool compresses to help reduce the ensuing inflammation.

He says that the patient must strictly practice sun protection (SPF 30)/sun avoidance, as well as gentle skincare.

Immediately following a PDT treatment, Dr. Bhatia likes to use a short course (one week) of a mild topical steroid twice a day, followed by two to three weeks of a hydroquinone or TriLuma Cream (fluocinolone acetonide 0.01 percent, hydroquinone 4 percent, tretinoin 0.05 percent, Galderma) post-treatment.