Everything you need to know about light-based skin treatment

You have probably heard of IPL and laser – are they the same thing? If not, how do they differ, and what are these treatments used for? To understand light-based therapy, we first have to understand light. So, what is light?

Light is a type of energy. The electromagnetic spectrum summaries the frequencies of light, respective to their wavelength and energy emitted. I’ve included a diagram below to help with the explanation.

Image retrieved from https://www.storyboardthat.com/storyboards/oliversmith/em-spectrum-chart

As we can see, radio waves constitute the lowest energy wavelengths on the spectrum, while gamma rays omit the highest energy wavelengths. When considering light-based skin rejuvenation procedures, wavelengths within the infra-red and visible light ranges are utilised.

After observing infra-red and visible light on the electromagnetic spectrum, clients will often ask “is exposure to this light harmful?” The short answer - no. Unlike ultraviolet, x-ray and gamma radiation, which are forms of ionising radiation that can stimulate irreversible cellular damage, the spectrums associated with light-based skin procedures are non-ionising and do not have the capacity to generate such cellular changes. Due to lower energy omissions, matter that makes up tissue are not at risk of irreversible damage via non-ionising radiation.

Mechanism of action

Now that we understand light, let’s take a look at how light can be applied to skin rejuvenation treatments. When we are performing light-based skin procedures, we are targeting what is known as a chromophore. A chromophore is essentially pigment that is found in the target tissue which can absorbs the emitted light. The tissue chromophore will differ based on the treatment being performed as well as the depth of penetration of the light (wavelength) necessary. For example, wavelengths selected for the treatment of sun damage and other hyperpigmentary conditions are targeting the melanin of the skin. Alternatively, haemoglobin of the blood serves as the treatment chromophore when treating capillaries and redness in the skin, while water is the target chromophore in resurfacing and ablative light-based skin treatments. The same principles are also applied to light-based hair reduction procedures, where the melanin of the hair follicle serves as a target chromophore.

With this in mind, care must be taken when performing light-based skin treatments, particularly those focusing on hyperpigmentary conditions, considering that the surrounding tissue (i.e. the skin that we are not targeting with treatment) also contains melanin. This melanin can present as a competing chromophore, absorbing the energy of the omitted light. For this reason, the relevant treatment parameters must be considered by an experienced therapist in order to deliver a controlled disruption only to the target tissue, while preserving surrounding tissue.

So, how is this possible? The controlled destruction of target tissue occurs in a process referred to as selective photothermolysis. During photothermolysis, light is absorbed by the treatment chromophore and converted into heat. This heat shatters the target chromophore into smaller particles, which are then metabolised and excreted from the body with the help of special immune cells called macrophages.

Simply put: photo = light / themo = heat / lysis = destruction

This process via laser is demonstrated below, where melanin within a hyperpigmentary skin condition is being targeted:

Image retrieved from https://www.odilaser.com/high-power-eo-q-switch-nd-yag-laser-for-pigmentation-tattoo-removal_p46.html

Since the highest concentration of melanin resides in the top surface layers of the skin, shorter penetrating wavelengths have a greater tendency to interfere with melanin in surrounding tissue. While this may not be a concern for fairer skin tones, darker skin tones have an abundance of superficially distributed competing chromophores therefore posing a greater risk. Longer wavelengths serve as a much safer option for darker skins as they have an ability to bypass the surface layers of the skin, avoiding the competing chromophores. However, it is important to note that certain pigmentary skin conditions require shorter wavelength selection which may not be suitable for those with darker skin types. Thorough consultation is therefore necessary in order to establish best treatment approach.

So, what can you expect to experience and what is the down time involved with light-based skin treatments? Treatment sensation can be best described as an intense flash of heat for the duration of the light pulse, which immediately dissipates. The down time depends on various individual factors, such as the client’s healing abilities, as well as what chromophore has been targeted and the severity of the condition. This will be advised during the initial consultation. Generally, after light-based skin treatments, the skin may feel hot and appear red, similar to that experienced after sunburn. Some clients may also experience swelling of the treatment area, which is why cool compresses in the days post treatment are recommended. Unique to the treatment of hyperpigmented skin lesions are the areas of darker skin and microcrusting (flat scabbing) that present on the surface of the skin, which can take up to two weeks to regenerate.

Difference between IPL and laser

Now that I’ve discussed light and it’s interaction in the skin, let’s compare Laser light and IPL light. The image below compares the characteristics of laser light and IPL.

Image retrieved from https://www.mechehair.nz/services/laser-hair-removal/

Essentially, laser emits a single wavelength of focused light, while IPL delivers a multiple wavelengths at once of scattered light.

Laser light of a single colour that is termed monochromatic. It also comprises of a single wavelength of coherent energy that flows in a single direction. Laser light has low divergence, meaning that emitted light travels in a parallel and synchronic manner, rather than propagating outwards.

Alternatively, IPL utlises multiple colours of light, which is referred to as polychromatic light. This light is also made up of multiple wavelengths travelling in a non-coherent, multidirectional manner. IPL exhibits high divergence meaning it propagates outwards.

Both modalities are widely used in skin rejuvenation procedures.

Contraindications to light-based skin treatments

Since ultraviolet radiation stimulates melanin production, sun exposure before or after lightbased skin rejuvenation stimulates post-inflammatory pigmentary changes and likelihood of adverse reactions. For this reason, sun avoidance is necessary throughout treatment. In saying this, it should be understood that many pigmentary conditions arise as a defense mechanism to protect the skin from the sun, therefore pigment removal and re-exposure of the treatment area to the sun is never advised. Other contraindications to treatment are thoroughly discussed in a pre-treatment consultation.

If you are interested to discuss your skin goals and establish your suitability for light-based skin treatments, book in for a consultation here or by calling 5916 1123!