DR. HIRSCH talks about triggered growth

"Some patients who undergo laser hair removal are experiencing disturbing hair regrowth on or near the treated area. To make matters worse, this new hair can be thicker, more abundant, and more difficult to treat.

Ranella J. Hirsch, M.D., a clinical instructor at Harvard Medical School in Boston, first reported this phenomena while a clinical laser fellow at the Wellman Laboratories of Photomedicine of the Massachusetts General Hospital. Tracking down these reports, Dr. Hirsch uncovered nearly 100 cases of this phenomena occurring and, to date, has verified nearly 20 reports of counterintuitive hair growth after laser treatment.

“They do seem to fall into a very specific subtype, which is for the most part women of skin types III and IV, mostly women of Mediterranean or Italian descent, who, after treatment for hair removal, usually at low fluences, develop a counterintuitive hair growth,” Dr. Hirsch said.

“I can fairly accurately predict the patients likely to be affected when I walk into my waiting room; I know these women when I see them now,” she said. They are usually of Fitzpatrick skin types 3 or 4 and initially seek laser hair removal to remove fine, downy hair in the upper neck, chin, and sideburn area. The hair regrowth most commonly occurs at or adjacent to the treated area and is often far thicker and more abundant than the original hair. Dr. Hirsch has heard of one fair-skinned woman who also had hair regrowth at sites distant from those treated and also of a case in a male, but these cases are by far in the minority.

Dr. Hirsch and colleagues have developed several theories as to why this regrowth occurs, but their prevailing one, supported by laboratory studies, is that treating patients at fluences that are too low triggers an inflammatory cascade that stimulates hair growth.

To date, Dr. Hirsch’s investigations suggest a pattern in which counterintuitive hair regrowth is much more likely to occur when patients are treated by someone with inadequate training on how to properly use a laser for the purposes of hair removal. Many patients with the problem were treated by non-physicians or physicians who are not specialized in aesthetic procedures. She says the complication is much less likely to occur by selecting the proper laser and parameters in the first place.

The primary cause of the problem appears to be treating darker-skinned women with too low a fluence. “Darker skin types really do need an aggressive amount of cooling and special care with choosing parameters,” Dr. Hirsch said. “Just as you don’t want to treat at too high a fluence and potentially get excessive blistering, you don’t want to treat at too low a fluence, either. I think that’s really the art of doing laser hair removal well. … There is no cookie-cutter mold. There is no one laser size that fits all.”

She recommends that anyone interested in performing laser hair removal undergo training that, at the very least, involves observing an expert perform the procedure and being themselves observed treating a variety of skin types by an expert. Learn about important parameters that are sometimes overlooked, such as pulse width. Also, understand how a laser works and do not rely on a sales representative or training video for complete instruction.

Individualize treatment - standard settings only work well on patients with the combination of very dark hair and very light skin.

Fortunately, once the damage is done, it is treatable. “These patients are manageable, but they must be treated with great care,” said Dr. Hirsch. “You’re actually going to wind up treating these patients with much higher fluences. There are very few people in our experience who have not been able to successfully have that hair removed, but if it took three sessions to grow the hair, it will take 13-15 to get rid of it. It’s resistant hair, but you can usually get rid of it.”

Dr. Hirsch emphasized that patients undergoing treatment for hair regrowth require careful but aggressive cooling of the skin. “The epidermis is going to take a very severe beating while you’re going after the newly grown hair.”

I had recently read an article in Dermatology Times about this issue, and they are just starting to do some serious studies on this phenomena. I am just guessing here, because the studies have not yet begun, but in reading the article you quoted, I believe the patients had been treated either with diode or alexandrite lasers, which have a greater affinity for melanin. Just as the doctor says, in order to safely treat darker skin types with these machines, you must use a much lower fluence than is effective for hair removal, or you risk blistering, crusting and scarring. The heat from the treatment will bring increased blood circulation to the treated area, and could stimulate hormonally-active hair growth (it does seem that the target area is always the face for this additional hair growth). None of this is an issue with a high-powered Nd:Yag laser. Higher fluences are effective for hair removal, but do not damage the skin. We are finding out that we can safely use much higher fluence/lower pulse widths on Fitz. V and VI without damage to the skin. It will be interesting to see the results of the study - I will keep you all posted on it as it comes out. Ciao! :wink: