Skin and Allergy News Online

S & A News Home

Back Issue Archive

Search

User
Pref

Help

Logout

Table of
Contents

Drug
Links

<<
Article

>>
Article

March 2001 • Volume 32 • Number 3

Dermatologic Surgery

All fluences being equal
Bigger Spot Sizes Yield Better Hair Removal Results

Betsy Bates
Los Angeles Bureau

DENVER — Larger spot sizes achieve significantly better results than smaller spot sizes when used at identical fluences during laser hair removal, Dr. Sorin Eremia reported at the joint annual meeting of the American Society for Dermatologic Surgery and the American College of Mohs Micrographic Surgery and Cutaneous Oncology.

"Most laser operators think of spot size in terms of convenience. A larger spot size is easier to overlap and results in faster treatment. But the true importance of spot size relates to scatter of laser energy as it penetrates the tissue," said Dr. Eremia, a Riverside, Calif., dermatologist.

He explained that spot size is of little clinical importance when the target is on the skin's surface. Hair removal is a different matter, however.

"With a target well under the surface of the skin, a small spot size ... would lose energy very quickly. If you start out at say, 40 J at the skin surface, [a] 4-mm spot size could only deliver 40 J maybe to a level of 1 mm under the skin." But a larger spot size would deliver 40 J to 2-4 mm under the skin, he said.

To determine just how big of a spot size is needed to remove hair efficiently, Dr. Eremia enrolled 15 patients in a study comparing hair removal in the axilla using the 755-nm alexandrite laser equipped with a cryogen spray-cooling device. A 3-millisecond pulse width was used. Each individual was tested prior to the study to determine the highest fluence he or she could tolerate, and that fluence was used throughout the study. An 8-mm spot size was used to treat half the axilla and a 12-mm spot size, the other.

Four treatments were delivered 4-6 weeks apart, and hair counts were performed 6 and 12 months after the final session.

"The results were quite impressive. The 12-mm spot size yielded far better results than the 8-mm spot size," Dr. Eremia said.

In regions treated with a 12-mm spot size, hair counts were reduced by 83% at 6 months and 84% at 12 months. Those treated with an 8-mm spot size saw a 56% lower hair count at 6 months and a 53% lower count at 12 months.

Skin type, hair characteristics, and energy fluence also influenced results.

At 25 J/cm² and 20 J/cm², for example hair counts were reduced by only 75% and 50% when a 12-mm spot size was used. With an 8-mm spot size used at 25 J/cm² and 20 J/cm², hair count was reduced by just 50% and 25%, respectively.