The Skin Benefits of Topical Vitamin C
Vitamin C is a naturally occurring vitamin antioxidant. It is the most abundant antioxidant in the human skin.  Most plants and animals are able to synthesize vitamin C from glucose. However humans lack the enzyme L-glucono-gamma lactone oxidase required for its synthesis.  So we must get it from natural sources like citrus fruits and leafy green vegetables.
What happens if we are deficient in Vitamin C?
Without sufficient Vitamin C this can result in Scurvy. Historically, vitamin C-rich foods like lemons were carried by sailors on long journeys to avoid Scurvy, which causes diseases like bleeding gums from reduced collagen synthesis, leading to connective tissue and blood vessel fragility.
How was Vitamin C discovered?
In 1937, Dr. Albert Szent Goyrgi was awarded the Nobel Prize for his work in isolating the vitamin C molecule from red peppers, and understanding its important role in the prevention of Scurvy. 
What is the difference between topical Vitamin C vs. Oral Vitamin C
The absorption of oral vitamin C through the small intestine is really limited. When we consume Vitamin C only small amounts of the drug is absorbed even with high oral doses. In addition the bioavailability of vitamin C in the skin is in adequate when it is administered orally [4,5]. But when we apply ascorbic acid topically (on top of the skin) the ascorbic acid will cross the epidermis into the underlying dermis more easily because of its low molecular weight.
Also, when the vitamin C products are made with a pH of 3.5 or less these are even more effective in absorption of ascorbic acid. So, topical vitamin C is much more effective when applied directly on the skin.
How do Vitamin C levels affect the skin?
Vitamin C is commonly found in the skin in greatest concentrations in the dermis and epidermis [6,7]. Aging however causes a decline in vitamin C content in the skin. In one study, aged skin was shown to have 70% less concentration of several antioxidants including L-ascorbic acid compared with young skin . In addition, exposure to oxidative stress via UV radiation, pollution and smoking can further lower vitamin C content .
Vitamin C as a photoprotector
Virtually all plants and animals protect themselves from the sun using Vitamin C and E which may protect against skin cancer and photoaging.  Vitamin C does not absorb UV light but neutralizes free radicals.
Why Vitamin C and Vitamin E work well together
Although vitamin C on its own is a great antioxidant and offers photoprotection it works best when combined with vitamin E, which multiplies its effectiveness 4 times.
How to ensure that your Vitamin C is pure and stable
Vitamin C serums are very fragile. When exposed to air or light the L-ascorbic acid oxidizes and the serum then turns an orange or brownish colour. Vitamin C serums should be clear to straw coloured for optimal performance. Vitamin C is usually sold in amber bottles to help protect the vitamin C from light. The highest purity of vitamin C is USP “United States Pharmacopeia”.
How to use Vitamin C
Apply vitamin C to the skin over taking it orally as this method is up to 20 times more effective. Apply once daily after cleansing in the morning to maximize vitamin C’s antioxidant and photoprotective properties. Use both Vitamin C and E together for increased antioxidant protection.
Recommended Vitamin C & E Products
A potent antioxidant serum to reduce the visible signs of aging. A unique delivery system ensures the 15% vitamin C complex is always optimally active. The vitamin C powder is kept separate in a unique cap and only mixed into the bottle of serum when you are ready to use it.
AlumierMD EverActive C&E™ + PeptideShop AlumierMD
1. Compound Summary for CID 54670067, PubMed Open Chemistry Database, NIH U.S. National Library of Medicine
2. Naidu KA. Vitamin C in human health and disease is still a mystery? An overview. Nutr J 2003;2:7.
3. Wikipedia: [Home Page] Vitamin C: History. Discovery and Sources in Available from: https://en.wikipedia.org/wiki/Vitamin_C.
4. Talakoub L, Nehaus IM, Yu SS. Cosmeceuticals. In: Alam M, Gladstone HB, Tung RC, editors. Cosmetic dermatology, Vol. 1. Requisites in Dermatology. 1st ed. Gurgaon: Saunders Elsevier; 2009. pp. 13-4.
5. Traikovich SS. Use of Topical Ascorbic acid and its effects on Photo damaged skin topography. Arch Otorhinol Head Neck Surg 1999,125:1091-8.
6. Shindo Y, Witt E et al. Enzymic and non-enzymic antioxidants in epidermis and dermis of human skin. J Invest Dermatol 1994;102:122-24.
7. Rhie G, Shin MH et al. Aging- and photoaging-dependent changes of enzymic and nonenzymic antioxidants in the epidermis and dermis of human skin in ivo. J Invest Dermatol 2001;117:1212-7.
8. Rhie G, Shin MH et al. Aging- and photoaging-dependent changes of enzymic and nonenzymic antioxidants in the epidermis and dermis of human skin in ivo. J Invest Dermatol 2001;117:1212-7.
9. Shindo Y, Witt E, Packer L. Antioxidant defense mechanisms in murin eepidermis and dermis and their responses to ultraviolet light. J Invest Dermatol 1993:100:250-5.
10. UV photoprotection by combination topical antioxidants vitamin C and vitamin E Am Acad Dermatol. 2003 Jun;48(6):866-74. doi: 10.1067/mjd.2003.425.