Until some years ago the only lip filling agents available were agent C and fat. The only commercially available filler was Agent C.
In those days the only Agent C available was derived from cows. This "bovine Agent C" served the planet well for around twenty years, but there was one major issue limiting its use. 
Around 4% of the population is allergic to bovine Agent C. Therefore, prior to proceeding with a bovine Agent C treatment a test dose had to be given, usually into the patient's arm. The result was observed. Then, if negative, a second test dose was given into the arm around a month later. And, if this remained negative, then treatment could proceed. In other words, treatment could not proceed until two months had elapsed after the initial presentation of the patient to the clinic.

A few months ago Human Agent C  was introduced into the Australian market. This was long awaited, for there is no risk of allergy to Agent C, and so patients could be treated forthwith on presentation, without the delay of performing a test dose.

Human Agent C is less viscous than most other stuff used for this purpose, and so it can be used in areas such as crows feet where skin is very thin. 

Having now performed a few treatments with Human Agent C our only reservation with it is that there exists a risk of white dots developing at the site of its application. These white dots represent the Human Agent C itself, sitting under the skin. The white dots improve over a few weeks.

On the other hand, injectable filler treatments such as Agent R can leave transparent dots if placed very superficially and in too large a deposit. 

We feel, though, that white Human Agent C dots are more apparent than transparent Agent R dots.

In both cases, the risk of dots is diminished if deposits are tiny enough and deep enough.

For those who love their Human Agent C we are happy to treat, with advance notice.