What is a LASER and How does Laser Hair Removal really work?

Let's start with the basics!! What is a LASER? Wikipedia defines a LASER as: A laser (standing for Light Amplification by Stimulated Emission of Radiation) is a device which produces electromagnetic radiation, often visible light, using the process of optical amplification based on the stimulated emission of photons within a so-called gain medium. The gain medium in a LASER is a material with properties that allow it to amplify light by stimulated emission. When the light energy reaches a certain amount then it is released in a beam. It is this beam and light energy that is then absorbed by the hair follicles and destroys the follicle thus getting rid of the hair in laser hair removal. Many different types of lasers exist and they all have different physical properties. You can read all about them on the web. Now that we know what a LASER is and does, we can begin to explore the anatomy and growth cycle of a hair follicle.... HAIR ANATOMY Hair has two separate structures - the follicle in the skin and the shaft. Follicle - The follicle contains several layers. At the bottom of the follicle is a projection. This projection is called a "papilla" and it contains tiny blood vessels, that feed the cells. The living part of the hair is the bottom part surrounding the papilla called the bulb. This bottom part is the only part fed by the blood vessels. The cells in the bulb divide every 23 to 72 hours, faster than any other cells in the body. The sebaceous gland is important because it produces sebum which is a natural conditioner. Sebum production decreases in women throughout their lives. The production also decreases in men, but not as much as in women. Shaft - The hair shaft is made up of keratin in three layers. The inner layer is called the medulla and may not be present. The next layer is the cortex and the outer layer is the cuticle. There are pigment cells that are distributed throughout the cortex and medulla giving the hair it's characteristic color. Laser energy is well absorbed by this dark pigment in the hair. HAIR GROWTH CYCLE Hair on the head grows only about 12 cm per year. At any given time, a random number of hairs will be in various stages of growth and shedding. There are three stages of hair growth: catagen, telogen, and anagen. Catagen - The catagen phase is a transitional stage. This phase lasts for about 2-3 weeks. During this time growth stops and the outer root sheath shrinks and attaches to the root of the hair. This is the formation of what is known as a club hair. Telogen - Telogen is the resting phase. This phase lasts for about 100 days for hairs on the scalp and much longer for hairs on the eyebrow, eyelash, arm and leg. During this phase the hair follicle is completely at rest and the club hair is completely formed. Pulling out a hair in this phase will reveal a solid, hard, dry, white material at the root. About 25-100 telogen hairs are shed normally each day. Anagen - Anagen is the active phase of the hair. The cells in the root of the hair are dividing rapidly. A new hair is formed and pushes the club hair up the follicle and eventually out. During this phase the hair grows about 1 cm every 28 days. Scalp hair stays in this active phase of growth for 2-6 years. Understanding the different growth phases explains why laser hair removal targets hairs in different phases when you get treated and why only some hairs are destroyed at any session. This is why you need to have multiple sessions so you can get all the hairs and catch them at different growth phases...The light beam that is emitted by the laser will target the hair follicle pigment and destroy it. After several sessions you have eliminated many hairs, all in different cycles of growth and now you are hair-free! JP Souaid, MD, FRCSC NeoDerma Clinic laser hair removal ottawa