Medix 5.5 Hyaluronic + CICA (Tiger Grass) Instant Hydration & Firming Serum. If your skin is dry, dull, sun-damaged, wrinkled, generally lacks luster then it is time to learn about pH balances and their effect on your skin. The key to beautiful skin is to maintain a healthy skin barrier with a pH of 5.5. Medix 5.5 promotes smooth, firm, healthy-looking skin by softening the look of fine lines and wrinkles.