Shedding of skin is a process call desquamation. In normal skin, the whole epidermis is replace in about 42 days and for the stratum corneum alone in about 14 days. That’s why you should allow at least 30 days to see if the product works or not. But if you have an immediate allergic reaction to a product, you should discontinue using it right away though.
Remember the protein bridges, desmosomes, that connect between cornecytes? Desquamation is the enzymatic process that dissolves those protein bridges and shedding of these cells. This process is opposite of the production of amino acids from proteolytic degradation of filaggrin proteins. The proteolytic enzymes responsible for desquamation functions need the stratum corneum to be well-hydrated. And these enzymes are located intercellularly. In the absence of water, the cells do not shed normally and the results is thick, dry, rough, and scaly skin. There should be a balance in the production of corneocytes and shedding. Increased production of corneocytes (as in psoriasis) or decreased shedding (as in ichthyosis) results in the accumulation of cells on the skin surface and dry, rough skin.