I'm extremely sorry. I don't know why I mixed Germal II and Germal Plus. I simply should not write anything after 22:00 O'clock
Anyway, as Irena has collected in the thread(so wonderful and complete ): Germal plus is a mixture of :
99% Diazolidinyl Urea and 1% 3-lodo-2-propynylbutylcarbamate Diazolidinyl Urea is a formaldehyde donor and formaldehyde donors are very active preservatives and relatively milder than formaldehyde itself, but they still cause sensitization:
These are only a few examples.
Now we come to the compatibility with Proteins.
In most of the product data sheets (unless they are provided by an honest manufacturer) it is mentioned that Diazolidinyl Urea (in our case Germal Plus) is compatible to almost all cosmetics ingredients
If you search more and are lucky to have success to original papers you'll see:
it's not inactivated by non-ionic emulsifiers and proteinswhich is completely true, the efficiency of diazolidinyl urea is not reduced by proteins and nonionics. However, it doesn't mean that proteins feel good besides diazolidinyl Urea (generally formaldehyde donors). Protein is degraded by formaldehyde and formaldehyde donors. It causes a change of color, phase separation, change of odor of the product. It may not happen immediately but within a couple of weeks depending on the conc. of individual components.
well, I'm not going to charge Germal plus. I can only relate my own story: according to my own carelessness, we had to destroy 5 tons of hair shampoo because I ordered adding a formaldehyde donor to a shampoo containing collagen. It's a long long time ago but the memory is still stabbing. The shampoo changed color from a beautiful pearly white to a disgusting brown with a horrible stink. I wish nobody to repeat this experience even for 50 gr of a lotion.
here another (not very updated ) link to preservatives: