Types of skin cooling

Skin cooling is an important part of aesthetic laser therapy. During photothermal treatments, skin cooling is needed to protect the epidermis. But apart from protecting the epidermis it can serve various other functions such as local anaesthesia and blood flow restrictor.

There are various forms of skin cooling available on the market, ranging from ice-packs to sophisticated equipment. The two most common forms of cooling are either cooling gels or cooling tips on the handpiece.

Thermal image of gel cooling.

When we look at cooling gels, which is the form of skin cooling that offers the least protection, you will find that it offers a benefit of ease for the therapist to slide the handpiece over the skin. The downside of gels is that the protection is extremely limited, and it is a consumable. Although the gel capture the heat initially, the heat remains in the gel. This means that the initial heat is drawn from the epidermis, but then gets locked in the gel layer, which cause a pre-warming effect on the larger area. The heat is not removed, but spread over the larger area.

Absorption curve for melanin, oxyhemoglobin and water between 300nm and 2000nm.

Then the question arises; why is it more comfortable for the client when gel is used? A part of the answer to this lays in the fact that gel reduces the energy that hits the skin. Water absorption starts to become more prevalent from 700 nm onward, 700 nm to 1200 nm are wavelengths commonly used in aesthetic laser therapy. By adding a layer of gel, which is mostly water, you add an energy filter. Additional to this, some gels also reflect the light.

Thermal image of active cooling.

The second most common form of cooling offers the most protection to the epidermis if used correctly, contact cooling. Best known is the cold tip on diode lasers. However, not all forms of contact cooling are equal. The most effective form of contact cooling is where you have pre-cooling, active cooling, as well as post-cooling. Pre-cooling is when the skin that is about to be treated is cooled down before the light pulse. Active cooling is when the skin is cooled during the pulse. And post-cooling is when the skin is cooled after the light pulse has hit the skin. Contact cooling is the most effective when all three components are present.

Thermal image of pre-cooling and active cooling combined.

Cryogen cooling is also proven a very effective form of skin cooling. The drawback with this form of cooling is that it is a consumable in the first place and that the equipment must be in correct functioning order to ensure that the cryogen pulse and light pulse are synchronized. The benefit to cryogen cooling is that it is easy to work with and the cooling is applied precisely.

Thermal image of cryogen cooling.

Finally, the last form of cooling we will discuss in this article is air cooling. This is when very cold air is blown over the skin during treatment. The drawback here is that you have an extra applicator. But depending on the machine, it may be possible to attach it to the laser handpiece. The benefit of air cooling is that you continually cool a larger area than just the spot size. Thus, you by default pre- and post-cool as well. Although, contact cooling remains the most effective way to extract the heat from a given area in the shortest period. Air cooling compensates for having default pre- and post-cooling.

Thermal image of air cooling.

Cooling is of utmost importance to photothermal treatments, but it also has a role to play during other types of photoreactions. Cooling is often used as a local anaesthesia during photoablative and photoacoustic treatments. In photochemical treatments heat and cold therapy is combined to control blood flow in the treated area.

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