Our Rating: 5 stars

A few years ago, you would have been likely to find me a bit negative on vitamin C – too drying, often irritating, usually not much effect. Recently though, I have become a convert by finding well-formulated vitamin C serums that use stable, potent and gentle actives. Medik8 CE-Tetra ($115 in the shop) joins them as a new favorite.

This pared back formula has vitamins C and E and that’s about it. What makes Medik8’s vitamin C serum a standout is that it has a 7% concentration of tetrahexyldecyl ascorbate. This form of vitamin C rates as potent, gentle and non-drying. It is stable, can be used in lower concentrations than some other forms of vitamin C and apparently also has the ability to stimulate the skin to produce glycosaminoglycans, natural moisturizers that allow skin to absorb moisture from the body itself.

Although the research behind tetrahexyldecyl ascorbate tells a good story, I haven’t found any to be independent. A study published in Dermatologic Surgery said that it "penetrates directly into the epidermis and dermis, acting both as an antioxidant and a direct stimulant of new collagen" was conducted by a company manufacturing the ingredient. Another by SkinMedica claimed it can provide five times greater penetration into keratinocytes and five times greater collagen production than ascorbic acid.

The proof, as they say, is in the using and I found CE-Tetra – which, of course, also has vitamin E – to be very effective, especially at taking down rough sun-damaged skin. I’ve been using it daily on my neck (Arcona’s The Solution Pads for exfoliating at night a couple of times a week) and feel that I am truly winning the battle. I should also mention that the jojoba oil base sinks right in. The unwanted (in my case) silicones give the serum additional slip and superficial silkiness. In any case, I bought a bottle as soon as I finished my tester.

Ingredients: Simmondsia Chinensis Oil, Tetrahexyldecyl Ascorbate, Cyclopentasiloxane, Cyclohexasiloxane, PPG-12/SMDI Copolymer, Tocopherol (d-Alpha)