I have found that using salt as an effective preservative in creams. I once experimented with making a comfrey cream which is very effective for bruises, sprains and broken bones. I used comfrey juice mixed in my cream base, but after a short while it became covered in a thick mould. I had heard that no bacteria can live in the Dead Sea because of its high salt environment, so I mixed salt in with the mouldy cream to see what would happen and "hey presto", next time I looked…no mould. The cream still has no mould or contamination even after almost two years!
High salt concentrations are needed to act as a preservative (10%). Sea water is only 3.5%, so that is pretty salty! The salt causes the microbes to rupture due to osmolarity. It can also effect the DNA and enzymes within the microbe.
Salt concentrations at this level is way too salty to eat, but salt is handy for cleaning and for non-edible needs. When we use the spiced salt polish in the second step of Queen Esther’s ritual, it kills bacteria on the skin and that is one of the main reasons you feel so clean and fresh afterwards.
Salt is also a great mould killer and eliminates spores without the need to resort to toxic harsh chemicals. Clove is even more superior to salt against mould and an effective bathroom mould killer spray cleaner can be made with 1/2 tsp of clove oil in 1 litre of salty water.