Vitamin A (retinol) is an excellently researched, highly regarded anti-­ageing substance, which is a must for any effec­tive product designed to care for skin that is showing signs of ageing. This makes it an essential part of TetCode4. Vitamin A is effective at inhibiting the enzymes that break down precious collagen, which lends the skin volume and elasticity. This means the collagen-­building activities prevail, so the skin can breathe a sigh of relief and remain naturally beautiful.