Photosensitivity

One of our laser course students called us recently. The report was that one of their clients, who had been undergoing a series of laser treatments, had recently come in for the next treatment with unexpected results. All had gone well previously at the documented treatment fluences, but this time the client experienced a heavy “rash” after the treatment. What was the problem? After discussion it turns out that this person had recently changed medications, and the most probable cause was that the new medicine caused them to be photosensitive, and therefore changed their reaction to their “normal” laser treatment.

Photosensitivity in People: Biological reactions to light. We normally experience this through our eyes which are obviously photosensitive - our vision is based upon light hitting our retinas and creating a chemical reaction that allows us to see. We experience this with Vitamin D synthesis in our skin - due to sunlight creating biochemical reactions. We experience this with suntans - due to the light of the sun stimulating our melanocytes to proliferate and giving us “brown” skin. Light reacts chemically with other things as well. Hydrogen Peroxide is stored in dark bottles so that light can’t get in and initiate a chemical degradation. Light can photo-chemically affect all things - eventually - one way or another. Low level light therapy creates subtle biological enzymatic chain reactions in our bodies to enhance healing and tissue regeneration.

In Laser and Light based cosmetic treatments photosensitive reactions of clients can create adverse reactions, and is an important item to screen for in the initial patient history.

Let’s be clear first. Even though it is well documented that some people are overly sun (light) sensitive, and that many drugs and foods create hyper sensitivity in some individuals, the exact mechanisms of these reactions are not entirely well understood. It is well documented that these reactions occur however, and many of these oral and topical agents can exacerbate light sensitivity. Ironically enough we tell clients to stay out of the sun prior to laser treatments to reduce adverse reactions and to use sunblocks before treatments. But some suncreens and blocks can actually create photosensitivity in some people. It seems to be different for everyone.

Photosensitivity can be generally relegated to two classes of reactions - Photoallergic and Phototoxic reactions. Photoallergic reactions are due to our immune system and are a generalized inflammatory response to sunlight. Picture a sun sensitive Type I skin type with red hair, light skin and freckles. They might get too much sun (or laser) and develop hives as a response (urticaria). Biochemical changes occur in the skin from the sun which the body interprets as a foreign body and inflammatory immune responses result - redness, swelling, and itching. In severe cases it can even elevate to anaphylactic shock (potentially life threatening). This can also occur after laser and IPL treatments. Some medical conditions also create this type of photosensitivity. It is extremely important in your patient history form to screen for “sun” sensitivity.

Phototoxic reactions can also occur - this is more like “local poisoning” of the skin rather than an immune response. The client has taken a drug or food which converts into a localized “toxin” in the skin once irradiated with light. A severe local reaction can result, including redness, swelling or even blisters. Sometimes this can be severe. There is some degree of overlap between photoallergic and phototoxic reactions due to biological mechanisms, but this article presents just a straightforward basic explanation of these reactions. It is also important to screen for these photosensitizing medicines and foods in the patient history form.

Remember though that not everyone reacts adversely to photosensitizing agents.

One of the more important functions of a medical director in an aesthetic laser/light practice is to create the patient history form to screen for these potential complications. More than this, it is important for each laser operator to be aware that various foods, drugs, cosmetics or even sunblocks can create photosensitive reactions in clients after laser/light treatments.

We can’t list all the drugs and foods that might cause photosensitive reactions in this short article, so we’ve posted most (not all) of them on our nonprofit website at www.LaserTraining.org, under “Resources” and then under the photosensitizers selection. That page also contains links to other good sites such as the FDA, Merck Manual, Medical Societies and others that contain good information on photosensitivity and photosensitizers, as well as photodynamic therapy.

A very wide range of foods and drugs can cause exaggerated reactions to laser & IPL treatments. Some of the major of these include NSAIDS (i.e. Ibuprofens), Antibiotics, Anti-Arrythmetics, Birth Control Pills, Retin-A®, Premarin, Anti-depressants, Chemotherapy agents, Corticosteroids, Endometriosis Management, Erectile Dysfunction (i.e. Viagra), Appetite suppressants, some sunscreens, fragrances & perfumes, and many others.

The Physicians Desk Reference (PDR) includes Photosensitivity in its Side Effects Index and lists the major photosensitizing agents. This is a great reference to have on hand in one’s practice to reference for unknown agents on your patient history form.

Photosensitivity may also be exploited as a therapeutic regime which utilizes photosensitizing agents and various light sources to create localized phototoxic reactions for either medical or aesthetic type treatments. This type of treatment is a photochemical process called PhotoDynamic Therapy, or PDT.

PDT was originally developed in the late seventies as a method for selective treatment of various cancers by Thomas Dougherty and his research staff at Roswell Park Cancer Institute in Buffalo New York. In this type of medical application the photosensitizing medication (photofrin®) is injected into a patients veins where it is distributed and absorbed throughout the body. By itself the drug is harmless and has no adverse effects in tissue. Normal tissues excrete the drug within 2-3 days, but it stays localized in the cancer or pre-malignant cells. The drug is still latent until it is activated by light. Because many of the anatomical sites to be treated are internal a laser is usually used in order to have sufficient intensity to be delivered through fiberoptics at clinically useful energy levels. A continuous wave red dye laser at 630nm is used because it penetrates farther into the tissues, even though blue light is a stronger activator of the drug. This light does not burn or heat tissue. It simply photo-activates the drug which becomes phototoxic to that particular cancer cell. Adjacent healthy cells are unharmed by the red light. The largest clinical series of multiple types of cancers is by Doctor James McCaughan (now retired from General/Thoracic Surgery) of the Medical Laser Research Foundation associated with Grant Medical Center in Columbus Ohio starting around 1982.

PDT first started being used to treat skin diseases in the early eighties by the Dermatologist Doctor Leon Goldman of Jewish Hospital and University of Cincinnati in Cincinnati Ohio. Doctor Goldman used a topical carrier to rub the drug into the skin rather than inject it systemically. Various light sources besides lasers may be used for external application such as the skin, and at the Medical Laser Research Foundation with Dr. McCaughan we used to even use Kodak slide projectors with filters. Treatment times were much longer but it worked.

More recently PDT has seen considerable growth in dermatological / aesthetic use utilizing the topically applied drug Levulan® (KeraStick®) and utilizing a non-laser blue light source to activate the drug. It is used medically to treat actinic keratosis (a precancerous condition), and cosmetically it is used for ACNE treatment and general skin rejuvenation. The photosensitizer is applied to the patients skin, which is then usually “wrapped” with saran wrap to seal and “bake” the drug into the skin for anywhere from 30 minutes to 2 hours, at which time the blue light is applied to the skin. The target for the drug in actinic keratosis are those pre-malignant cells, for ACNE it is the P. Acne bacteria in the sebaceous glands, and for general skin rejuvenation it is simply the deep dermal inflammatory reaction that occurs with subsequent healing and enhanced collagen production.

A natural form of PDT also occurs to a lesser extent in the treatment of ACNE with IPL’s and lasers such as the pulsed dye and copper bromide yellow light lasers. The P.Acne bacterium already contains a natural photosensitizer called Protoporphyrin IX (PpIX) which can be activated by these other light sources. ACNE may be treated with Laser or IPL in this manner without adding any exogenous photosensitizer, or you can do them as combined treatments for an enhanced effect.

The next frontier for PDT as a photosensitizing agent may very well be for Laser Assisted Hair Removal to treat white, grey or blonde hair (actually any color). Doctor Rox Anderson of Wellman Research Laboratories in Boston showed many years ago that PDT for cancer treatment using CW red light lasers could also kill hair follicles. It seems that the photosensitizer localizes in the hair follicle and bulb without regard to pigment. The red light from a CW Laser then penetrates deeply enough to activate the drug. This is phototoxic to the hair bulb and destroys it without damaging surrounding skin. A paper within the last couple of years at the American Society for Laser Medicine and Surgery meeting explored this option but found that the PDT with blue light treatment had no effect on hair removal. It was pointed out however that the blue light does not penetrate deeply enough into skin to effectively treat the hair bulb, and that red light from a CW Laser would have probably been effective. We’ll see.

Gregory T. Absten, Professional Medical Education Association, 800-435-3131. www.LaserTraining.org .