Cooling Mechanisms

All lasers use cooling mechanisms. As a general principle, heat dissipates by diffusion. If a chromophore, in this case the melanin pigment in the hair follicle, is heated beyond its capacity, the heat will be diffused into surrounding structures. Since light energy from the laser is converted to thermal (heat) energy, cooling mechanisms are needed to prevent thermal damage (burns). Cooling mechanisms protect the surface of the skin, skin structures between hair follicles, lower the risk of blistering and pigment changes, and cause less pain and swelling. Cooling also allows higher fluences to be used for more effective results. Darkly pigmented skin can also be treated more safely.

There are several basic types of cooling mechanisms used with lasers. There are advantages and disadvantages to all of them. Cryogen spray is a popular method of cooling for several reasons. It delivers consistent, effective cooling that is extremely easy to use and is not messy. Cryogen is a refrigerant at -30 to -50°C that is sprayed onto the skin before and/or after laser irradiation. Although it is possible to decrease the effectiveness of treatment and cause skin freezing/blisters if too much cryogen is used, most operators consider the cost of this consumable item the bigger disadvantage. Air cooling is also very effective with minimal side effects, but this method requires a large standalone machine. Cooling gels are the least effective cooling mechanisms. This method is prone to uneven application of the gel and potentially inadequate cooling. It is also extremely messy and only provides short-term, superficial effectiveness. Contact cooling can be very precise and effective. This method uses a cold gliding hand piece over a gel, but it is more difficult to use and requires a more experienced operator.

Most lasers come with their own predetermined cooling mechanism. Contact, cryogen, and air cooling are all sophisticated technology with minimal adverse effects. The most important goal for a consumer is to pick an experienced physician who understands the different methods and can match skin cooling to the task, laser, and patient at hand. The physician must also be very comfortable with the technique used, especially if contact cooling is the preferred cooling method.