Question: What is the most dangerous material towards human skin?

Christopher Bullock answered on 13 Jun 2017:

Hi Jennifer,

Lots of things are pretty dangerous, As I am sure you know things that are really hot or cold will burn skin. Equally liquids with really low or high pHs. There are also poisons that can be adsorbed through the skin and can kill.

My job involves designing things that are supposed to be implanted inside the body. This is where things get a bit more complicated. Not only do you have to be concerned with whether the materials you are using are poisonous but you also need to know whether they cause inflammatory reactions – this is where your own body responds to something you have implanted in the same way it does with allergies and it can be fatal. As your body is full of chemicals, you also have to consider whether it will react and degrade. The products of these reactions may have completely different properties to the original material and this also has to be considered. For example, there is a type of plastic called PMMA that is commonly used in bone surgery. Big pieces of this material are very safe but if it gets broken down into very small pieces (100x smaller than the width of a human hair), it can become toxic. Implanted devices degrading like this can obviously prevent them from working properly
but in some cases you actually want these reactions to happen. For example, doctors now use stitches that safely dissolve away inside the body after a few weeks, meaning that you never have to have them removed.

The ultimate goal is to design materials that work with the body so that it actually works better (heals faster for example) rather than just being safe.