Yellowish dullness in the skin, meaning that the color tone of the skin becomes to show yellowness with ageing, is simply called “skin yellowness”, hereinafter, unless specified otherwise, and it is considered problematic in the art in terms of skin care. It was once said that the denaturation of proteins in the skin was a major factor of inducing skin yellowness (i.e., saccharification or Maillard reaction); however, nowadays, it is said that the denaturation of proteins in the dermis, existing in a deeper part of the skin (i.e., carbonylation), would be such a major factor.
Since skin transparency may be deteriorated as the increase of skin yellowness and this may tend to make you look older than your actual age, measures against skin yellowness are distinctly important to keep your youthful appearance. As an actual example of such measures, Patent Literature 1 discloses an agent for inhibiting skin yellowness, which consists of a pumpkin seed extract, while Patent Literatures 2 and 3 disclose external dermal agents which contain a plant extract having an inhibitory effect on skin yellowness. Thus, conventionally known agents, including those which are disclosed in Patent Literatures 1 to 3, are the ones for avoiding skin yellowness by inhibiting denaturation, i.e., saccharification or Maillard reaction, of proteins in the skin.
Patent Literature 4 discloses a carbonyl-inhibitor for proteins, which contains one or more effective ingredients selected from an olive leaf extract, hydrolyzed pear protein, and lemon extract, and which inhibits neither glycation reaction nor Maillard reaction but inhibits carbonylation so as not to induce yellowness in the skin.
As described above, conventional measures against skin yellowness are agents for inhibiting saccharification or Maillard reaction of proteins in the skin so as not to induce yellowness in the skin, meaning that they are so to speak agents for preventing skin yellowness. Thus, it has been made efforts for inhibiting the formation of skin yellowness because it has been recognized in the art that the once-generated skin yellowness could not be diminished to restore the skin to its original condition.