Vitamin C.

"This is a really good place to start if you're thinking about starting vitamin C and you've never done it before. It's got 15% ascorbyl glucoside, which is a beautiful derivative vitamin C. It also has vitamin E. I really like this as a simple cheap vitamin C. You don't get additional benefits, but you are getting what you pay for, which is better than I can say for a lot of the products I'm looking at right now."

"The reason I'm calling this out is because they don't disclose the percentage. There is no point putting a vitamin C on your skin if you don't know what strength it's in. That's because vitamin C is a little bit on the irritating side. You need to know what you're using. If you have a very sensitive skin type, you're going to want to go in for something in a 5 to 10% concentration. If you have a very resilient skin type that doesn't irritate easily, you can go up to a 20% concentration to get the best results. But if you don't know what's in a product, how can you possibly match it to your individual skin's needs? You're just wasting your money and you're running a whole lot of risks. I would avoid any vitamin C that doesn't disclose the percentage. And The Inkey List are one of those. The Inkey List aren't particularly transparent. They don't go in big for percentages where it matters. They'll happily share a percentage of an ingredient which doesn't really matter what strength it's in, but they somehow hide the ones where it does matter. I would avoid."