One way to tell if you bath and body products are natural is to look at the expiration date. One of the primary reasons that so many lotions are made out of #petrolatum, mineral oil, #glycerin, and other synthetics is that petroleum byproducts and chemicals don't go bad. Bacteria can't grow in, let alone breakdown, chemical and petroleum laden products. This makes them really easy to work with as you don't have to worry about inventory. However, if a product can't be readily broken down by bacteria, it definitely is not natural. If bacteria can't use it, what makes you think that your skin will find use in the #product?
The truth is that the more #chemicals and synthetic components, the more stable the product is. Body lotions and other skin care products that contain natural ingredients are generally regarded as better for the skin. This is because the oils and butters help to create the same moisture barriers as unnatural products like mineral oil and petrolatum, but they can also be absorbed by the skin and used by the skin build up and repair itself. However, natural oils come from plants, trees, etc., which means they don't come sterile, and fats and oils make great #food sources. As a result, they are less stable and generally have a shorter shelf life.
This does not mean that natural skin care products make bad products; it only means that natural bath and body products have a shelf life. It is the same with nearly anything in your refrigerator. There is nothing in your refrigerator that is completely sterile. If it was expected to be sterile, it could be stored outside the refrigerator, and the more natural the product, the less time it takes for the bacteria to break down. That is why it takes 1 week before fruit and vegetables go bad, but your mayonnaise will likely never go bad. The same is true of your bath and body products. The more natural components and the more water present, the less time it takes for your bath and body products to "go bad." Going bad, however, is really only a term useful to the manufacturer or the retailer which means that the product no longer looks suitable for selling. The truth is that the product is still likely just as good as before, though it might need a quick shake before use.
The manufacturer takes many steps to extend the shelf life of their products. This includes the addition of preservatives. Preservatives can be anything used to extend the shelf life of a product. Not all preservatives are bad, though some can be. Vitamin C and vitamin E happen to be two very common preservatives. Both are strong anti-oxidants which help to extend the life of foods as well as bath and body products. Other preservatives include acids to reduce pH, salts to increase salinity, and metabolic inhibitors such as parabens. In bath and body products, the primary purpose of preservatives is to reduce the ability of bacteria to grow, and natural products almost always have some type of preservative. However, to be a 100% natural bath and body product means that the preservative used must also be from a 100% natural source. The key to look out for is when synthetic chemicals are used as the preservatives. Preservatives like parabens are petroleum derived and carry structures similar to agents known to cause cancer, increasing the fear that they will causing damage to your body.
When searching for bath and body products, more natural products are expected to have a shorter shelf life. Less stable is a good sign, and if you stick with products with a shorter shelf life you can be more confident that your products are natural and well tolerated by your skin.