Tyndall Effect & The Blanching Technique

In aesthetic medicine, the term Tyndall effect has been adopted from its original optical context to describe a bluish discoloration of the skin that can occur when hyaluronic acid (HA) gels are placed too superficially. Although frequently referenced, it remains a poorly understood and complex phenomenon in clinical practice.

To better understand the concept of the Tyndall effect, it is helpful to revisit the basics of the electromagnetic spectrum.

The electromagnetic spectrum includes all types of electromagnetic radiation. There are seven types of electromagnetic waves, which can be thought of as different forms of light emitted by objects around us – from the sun above, the ground below and even manufactured sources.

Types of Electromagnetic Radiation

Larger wavelengths are associated with microwaves, while shorter wavelengths correspond to x-rays and gamma rays.

A small portion of this spectrum encompasses the waves of white light, or sunlight.

White light is a combination of many colours, although only a small number are visible to the human eye. This band of visible colours is known as the visible spectrum. A simple demonstration involves shining white light through a prism, which splits it into its constituent colours.

The constituent colours of white light are red, orange, yellow, green, blue, violet, and indigo.

As one moves from violet and indigo towards orange and red, the wavelength of colour increases. Violet has the shortest wavelength, while red has the longest.

Rainbows provide a natural example of this phenomenon, as raindrops act like tiny prisms, splitting sunlight into its component colours.

The refraction through

raindrops mirrors that seen

in a prism, and the visible

colour spectrum appears

on the opposite side of

the droplets. This is then

reflected back into the sky.

The phenomenon partly explains why the sky

appears blue. The first steps towards correctly

explaining this were taken by John Tyndall in 1859.

Tyndall discovered that when white light passes

through a clear fluid containing small particles in

suspension, blue light is scattered more strongly

than other colours.

The phenomenon is referred to as the Tyndall effect, although physicists more commonly know it as Rayleigh scattering, named after Lord Rayleigh, who studied it in greater detail a few years later.

The following example provides a clearer understanding of this.

If the wavelength of each colour in the visible spectrum is imagined to correspond to the diameter of a particle of that same colour, a comparison can be drawn: violet has the smallest wavelength and diameter, whereas red has the largest.

If a particle is larger than the wavelength or diameter of red light, it reflects all the colours of light equally, and the scattered light appears white. When sunlight encounters larger particles like dust or smoke, all colours scatter equally, resulting in white scattered light.

If particles have a shorter wavelength or diameter than violet, the wavelengths of the smaller colours in the visible spectrum (indigo, violet and blue) are known to be scattered more strongly than the those of the larger colours (orange and red).

This is relevant because

the Earth’s atmosphere is

primarily made up of oxygen a

nd nitrogen molecules,

which are much smaller than

the wavelengths of visible

light. As a result, they scatter

shorter wavelengths—such as

violet, blue and indigo—more

effectively than longer ones.

The human eye contains three types of colour receptors, or cones, sensitive to red, green, and blue light. Thus, even though violet and indigo scatter more than blue, as they are smaller, it is primarily blue light that the human eye detects, thus explaining why the sky appears blue.

The Tyndall Effect in Skin

In skin, the Tyndall effect is thought to occur when HA gel is injected too superficially — with the filler sitting close to the skin’s surface rather than at a deeper plane. Light interacts with the gel particles similarly to how it interacts in the atmosphere: scattering shorter blue wavelengths and resulting in a bluish tint visible through the skin.

This discoloration usually presents as either:

• A thin line, often seen with linear threading techniques, or

• A localised area corresponding to a bolus injection.

However, there is ongoing debate about whether this explanation is entirely accurate. The particles that make up HA gels are considerably larger than the wavelengths of visible light, suggesting they should reflect all wavelengths equally, rather than selectively scattering blue light. As explained previously, this means they should reflect back white light.

Other factors may contribute to the phenomenon, including:

• The thickness of the skin — particularly in the tear trough region, which has some of the thinnest skin on the body.

• The interaction of light with the layers and structures of the skin, such as blood vessels, when distorted by HA gels.

Complicating matters further, there is limited guidance regarding which specific HA gels are more likely to cause this issue. Although it is well recognised that particulate fillers should be avoided when injecting superficially, non-particulate fillers have also been associated with the so-called “Tyndall effect.”

Blanching Technique

Adding further confusion, some fillers do not produce the Tyndall effect when injected superficially. One brand can even be used specifically for superficial injections using a method known as the blanching technique. The blanching technique involves a series of point-by-point microinjections into the superficial dermis. It is called “blanching” because the superficial dermis (at the junction with the epidermis) separates slightly, creating a white blanching effect on the skin.

The HA gel avoids producing a blue-grey hue due to its unique manufacturing process, which involves two types of cross-linking during production. This particular HA gel has other properties such as cohesivity, viscosity, and G’ (G prime) which play important roles in making it suitable for superficial placement.

While the blanching technique can produce outstanding results, it can be challenging for practitioners to become proficient with. To address this, the LW Aesthetics Academy has developed a specialised training course, simplifying the method and teaching an adapted version known as the Modified Blanching Technique.

As for the so-called ‘Tyndall effect’, it is almost certainly a misnomer. However, until a more accurate explanation becomes widely accepted, the term will remain in common usage.