The short answer is yes, in fact it could help the sensitivity, but it does depend on what causes your skin to be sensitive, how you apply it, which type of. vitamin C you apply and what else is in there.
I’m not sure whether you want to use it in an attempt to decrease the sensitivity of your skin, or that your skin is generally sensitive and you need to know that vitamin C isn’t likely to further irritate it. Your skin could be sensitive for a variety of reasons, from a reaction to a shower gel, to a perky immune system that doesn’t like anything it doesn’t already know. The latter should be respected and given low concentrations of whatever you try!
Eat it before you try!
Before giving you the topical options, I would just say that consuming vitamin C is the most effective way to address a deficiency and the potential associated skin problems.
The symptoms of too little vitamin C include poor wound healing, which affects collagen formation in the dermal layer - collagen-formation is carried out by fibroblasts which depend on vitamin C to stabilise the collagen molecule and stimulates its production. Older people and those with sun-damaged skin do seem to have lower levels.
Bear in mind that most trials on topical applications used people who either have a vitamin C poor diet or were know to be deficient. In either case, eating it is the most effective way to restore it. In a recent trial, the concentration of vitamin C in skin keratinocytes was seen to double when the subject took supplements, until blood plasma was saturated, then there was no more improvement in skin up-take.
However, when someone has low plasma levels, using a vitamin C cream or serum can also deliver the lacking vitamin C into the epidermal layer. There is usually at least three times as much vitamin C found in the superficial epidermal layers, so this would suggest it is probably worthwhile. There is markedly less found in the outer layer of the epidermis, which may be because the layer in contact with environmental stress factors lose vitamin C faster.
Another consideration is that people vary in how much they need in the skin for it to function optimally - the limited information on this would suggest a ten-fold differential. So, the vitamin C question is not a simple one….
Can it make sensitive skin worse?
When all other factors are considered and you have found a vitamin C serum you like, do use it as directed. As a rule, if the colour darkens, throw it out. You really don’t want to apply oxidised vitamin C to sensitive skin. Some topical treatments are white, some cream, some yellow, but whatever shade they start at, keep an eye on it becoming more orange. You will help slow the oxidisation (it is inevitable, it will oxidise in time) is to keep the lid tightly closed, keep it out of sunlight and try to keep it cool - under 15ºC and optimally, it likes to be between 5ºC and 10ºC. Directions on the pack will give you more specific guidance.
Are there less irritating possible alternatives?
If you are concerned that it may irritate your sensitive skin, there are alternatives you may want to consider. These can offer similar benefits, without such a risk of irritation.
Niacinamide is a good antioxidant and often better tolerated than vitamin C.
Curcumin and flavonoids (polyphenolic compounds found in plants with vitamin C). I often use this combination. The flavonoids may increase the bioavailability of the plant’s vitamin C, but more studies are required. But the carotenoids stay active for much longer and can help to even-out the complexion, reduce inflammation, and can fade hyperpigmentation. They can improve free-radical damage -specifically, the breakdown of collagen and elastin.
A-arbutin and kojic acid are again gentler, and when used at sensible levels, fade sun-spots and brighten the complexion generally without adding irritation.
PHAs - gentler than AHAs and can also be surprisingly good at improving the complexion generally.
So if you choose vitamin C, which C to choose….?
L-ascobic acid is the best researched, but this must be formulated in a cream where pH levels are below 4 to keep it safe and effective - it needs to get into the skin, but it needs to be kept from oxidising, which it is constantly trying to do - and this is it’s greatest disadvantage. If that can be avoided, it works well and offers some UV protection. Whether your sensitive skin will be happy with the pH is another matter, you will have to try it to know.
Lots of other derivatives have been developed to avoid the restrictions l-ascorbic gives formulators. Whatever form you choose, it has to be converted into ascorbic acid on the skin to be effective. Those that seem to be more stable, may not get very far into the skin and being stable doesn’t mean it converts well into useable ascorbic acid.
Adding a phosphate group (Sodium Ascorbyl Phosphate, Magnesium Ascorbyl Phosphate), does make it more stable, less inclined to oxidise and is happy in a pH up to about 7. It can be converted to ascorbic acid, but slowly and it seems to be poorly absorbed. Ascorbyl glucoside is another one, it is nice and stable and gets into the skin better, it probably offers UV protection, but there is little research on it’s ability to convert into ascorbic acid.
Some are delivered in an oily carrier, which should be more comfortable on sensitive skin and, in theory, should get absorbed. But the jury is out as to how stable it is and whether it converts effectively into ascorbic acid. But as mentioned earlier, if you just want to increase the skin’s vitamin C stores, overwhelmingly, the answer is - eat it! With that said, topical application can do more than just increase stores. It is often used for various reasons.
How much is enough?
Most studies are carried out in labs, inside glass dishes, not on people. In these conditions,15% seems to be optimum, if you want the maximum absorption to replenish low depleted vitamin C - if you live in a Petri dish and don’t mind the discomfort!
Outside the laboratory, it is effective from roughly 0.25% to 10% - depending on what it is formulated with, how it is prepared and partly as people vary such a lot in what they can tolerate and what they need. For sensitive skin, I would start low; 2% and see how that feels. I tend to use 3% to 8%, depending on what I’m putting it in.
When to use it?
Typically it was used during the day, partly due to its sun-protection properties. However, research has demonstrated that the body tends to repair free-radical damage during the night (or at least, whilst you are asleep), so it can be used at either time or both.
So, alone or in company?
I use it with plant extracts for the polyphenols and add extra vitamin E and ferulic acid -as these appear to boost the effect. look out for it formulated with soothing ingredients and others that can be busy helping it.
Don’t use it with anything that might add to the irritation - so AHAs, BHAs, PHAs, Vitamin A etc.
There is so much discussion on topical vitamin C, it is hard to know what, exactly you are using it for - only use anything if you know why you need it. Marketing is a persuasive art, try not to be persuaded to buy products your skin doesn’t need and look at other, less fashionable alternatives.