Even though there is no expiry date written on the bottle, this is done for a reason. This product boasts the most advanced formula of stable bio-available Vitamin C, Stay C 50. This means that while the natural properties of the product are retained, the product is prevented from oxidizing (expiring) rapidly. The process of “yellowing” of the product is exactly this process of oxidation which occurs when Vitamin C is left exposed to air. Therefore the stable formula of Kleem Jeunesse enhanced Vitamin C serum will remain fresh and effective for its whole duration. Secondly, thanks to the airless bottle, oxygen and bacteria are not allowed to come in contact with the product at any stage therefore ensuring the product’s freshness and sterility.