Lasers target a type of melanin, the stuff which gives hair its color. Think of it like a car in the sun. If a car is white, yellow, or red, it’s not going to get as hot in the sun as a car that’s brown or black. That’s because darker colors absorb more light and therefore heat up more.
There are two types of melanin: pheomelanin, which makes hair look blonde if there’s a little, or red if there’s a lot. If you’ve ever used yellow food coloring, you know it looks kind of red in the bottle, but looks yellow if you spread a drop out. Laser doesn’t heat up pheomelanin very well, because even when it’s really concentrated, it’s not very dark.
The other kind of melanin is called eumelanin, and in its pure form it looks pitch black. The less and less eumelanin you have, the more brownish your hair will look. This stuff absorbs a ton of light, so when you hit eumelanin with a laser, the blast of light causes your hair to heat up super-fast. This rapid heating can cause damage to the hair follicle if enough light is applied with the laser. The heat and the miniature shock wave caused by the blast of energy can actually break open cells in the area. If done right, it can damage the hair growth cells while sparing the cells nearby.
That’s also why people with darker skin or tans have to be careful. Their skin has more eumelanin, and the laser can’t tell the difference between eumelanin in hair and eumelanin in skin. It heats them both up, so if you have dark or tanned skin, the laser can burn your skin the same way it burns your hair. That’s why those clients have to use special lasers performed under the most cautious of circumstamces. The risk of serious skin damage is much higher.
So, to summarize your chances of permanent laser hair reduction if done properly:
black hair: best laser candidate
dark brown: good
light brown: not that great
reddish-blonde: very poor
blonde: no good
gray or white: not a chance
[ November 08, 2002, 08:30 PM: Message edited by: Andrea ]