First of all, we need to clarify where and when this problem occurs. For bruising after hyaluronic acid filling, it is mostly seen in hyaluronic acid filling tear trough, which we clinically call as Tyndall phenomenon. In the process of light propagation, when light hits a particle, if the particle is greater than the wavelength of the incident light many times, the reflection of light occurs; if the particle is smaller than the wavelength of the incident light, the scattering of light occurs, and what is observed at this time is the light wave surrounding the particle and radiating light around it, called scattered light or emulsion light. The Tyndall effect is the phenomenon of light scattering or emulsion. Some candidates have dark circles under the eyes, poor blood circulation under the eyes, or the skin in the tear trough itself is colored, and after hyaluronic acid filling, the dark circles are further aggravated due to the light refraction, so for tear trough filling, I suggest choosing collagen or fat gel. For whether hyaluronic acid filler will bruise in other locations, it depends on the overall amount of filler. For example, if the temples are particularly sunken and too much light is refracted, the problem of bruising may also occur. However, the skin in this location is often thicker, so the chance of occurrence is not very high. If the skin is bruised after the injection, we should suspect whether the injection has punctured the blood vessels and caused local bruising. If there are symptoms of bleeding after injection, you can press it for a while and then apply a cold compress, in this case there is often only a small piece of local bruising, and there will not be a large bruise, the post-operative recovery is relatively fast, do not worry too much.