From the Guidelines
Topical vitamin C can be irritating due to its acidic nature, which disrupts the skin's natural barrier and causes irritation, especially in sensitive skin. The concentration of vitamin C in a product significantly affects its potential for irritation, with higher concentrations (typically above 15-20%) more likely to cause stinging, redness, or dryness 1. Some key points to consider when using topical vitamin C include:
- Starting with a lower concentration (5-10%) to minimize irritation
- Applying to dry skin to reduce the risk of irritation
- Gradually increasing usage frequency to allow the skin to adjust
- Considering the use of vitamin C products at night when skin sensitivity is typically lower
- Pairing vitamin C with hydrating ingredients or using buffered formulations to reduce potential irritation while still providing antioxidant benefits. It's also important to note that the form of vitamin C matters, with L-ascorbic acid being the most potent but also potentially the most irritating, while derivatives like magnesium ascorbyl phosphate or sodium ascorbyl phosphate tend to be gentler 1. In terms of minimizing irritation, the most recent and highest quality study suggests that careful consideration of the concentration, formulation, and usage frequency of topical vitamin C is crucial to avoiding irritation and maximizing its benefits 1. Some studies have shown that certain ingredients, such as salicylic acid, can enhance the efficacy of topical treatments, but care must be taken to avoid inactivating other ingredients, such as calcipotriene, due to acidic pH 1. Overall, the key to using topical vitamin C effectively while minimizing irritation is to start with a gentle formulation, gradually increase usage, and pair it with hydrating ingredients.
From the Research
Topical Vitamin C Irritation
- The provided studies do not directly address why topical vitamin C can be irritating, but they do discuss the challenges and limitations of using topical vitamin C formulations 2, 3, 4, 5, 6.
- The instability of ascorbic acid, a form of vitamin C, may contribute to irritation or reduced efficacy in some topical formulations 3, 6.
- The studies suggest that derivative molecules and stabilization strategies have been explored to facilitate the incorporation of vitamin C into dermatological products, but more research is needed to fully understand their effects 3, 6.
- Some studies mention the importance of standardized parameters and in vivo efficacy tests to better elucidate the effects of topical vitamin C derivatives, which may help identify potential irritants or optimize formulations 3, 4.
- While the studies highlight the potential benefits of topical vitamin C, including antioxidant, photoprotective, and anti-aging effects, they do not provide a clear explanation for why it can be irritating in some cases 2, 5.