As we get older our skin gradually loses its collagen, elastin and hyaluronic acid. These are all made deeper in the skin known as the dermal layer. Collagen gives it strength, elastin makes it supple and hyaluronic acid gives it volume and helps to plump it out. That's why we develop wrinkles.
Our skin is designed to protect the body by acting as a barrier to the entry of harmful substances, so cosmetic products applied to the surface will simply sit there unless we can help them to reach the dermal layer.
There are two options. We can either treat the skin to make it receptive and more permeable to nutrients so they reach the dermal layer, or stimulate the skin to make more of its own collagen, elastin and hyaluronic acid. Dermaplaning, peels, radio frequency and electroporation, all help to make the skin more permeable to products. Plasma therapy and PRX stimulate the skin to make more of its own natural collagen and elastin.
Collagen is a protein and like any other protein if it's eaten it will be digested by stomach enzymes to amino acids. It will not reach the dermal layer. Creams will simply help the collagen to sit on the surface. Remember our skin is designed to keep things out.