I found this on the web
“Benzyl Alcohol (BA) is used to increase the lipid solubility of esterfied compounds and to prevent bacteria growth in the oil. Most UGL's use excess BA or only BA as the co-solvent, due to it's modest price. Unfortunately, it can cause the destruction of cells and significant localised pain and inflammation. The discomfort is characterised by fairly rapid onset of a painful, red, swollen area.
The shorter an ester, the less solubility is has in oil. This necessitates higher concentrations of BA to prevent the compound from 'crashing' out of solution. When the oil is injected, the BA is absorbed from the location of the oil depot. This caused the active compound to precipitate fine crystals within the muscle. The onset of this pain is often 4-12 hours after injection and is characterised by a hard, red, swelling at the injection site. To prevent this an additional co-solvent is needed, Benzyl Benzoate. BB maintains solubility of the esterfied compound past the point at which BA has been removed, preventing crystaline precipitation. Most UGL's don't add this to their compounded oils due to the higher cost. If added at approximately 20% by volume you can prevent most associated short ester pain.”
“From what I have read, BB is a solvent, so it melts some compounds. And as the result, it will keep a solution from forming crystals aka "crashing" and make it hold.”
