Maximum Usage Percentage of Ingredients: Per Formula or Cumulative?

The maximum usage percentage listed on the website for each active ingredient refers to the percentage within a single formulation, not the total percentage across all formulations applied at the same time.

However, as the staff mentioned, applying multiple formulations containing the same ingredients means your skin is exposed to a cumulative amount of those ingredients. If this cumulative amount exceeds the recommended maximum percentage for a single formula, it can increase the risk of adverse effects, particularly irritation.

Regarding your specific examples:

• Safe-B3™ (Niacinamide) and GlucoBright™: Using these ingredients at maximum rates in multiple formulas, leading to a cumulative percentage exceeding the single-formula limit, can increase the risk of skin irritation, as confirmed by the staff.
• PE-1 Aqua and 1,2-Hexanediol (Penetration Enhancers): Exceeding the recommended usage per formula, even cumulatively, may not necessarily improve overall penetration further and could potentially cause irritation or other adverse effects due to increased exposure to ingredients that can affect the skin barrier.
• Phenoxyethanol SA (Preservative): The maximum usage limit for a preservative is primarily to ensure the stability and safety of each individual formula and to stay within regulatory guidelines for a single product. However, cumulative exposure to preservatives from multiple products applied simultaneously could potentially lead to increased risk of skin sensitivity or irritation in susceptible individuals.

In summary, while the percentage limit is per formula, exceeding that limit through cumulative application of multiple products containing the same ingredients, especially those known to cause irritation, increases the risk of negative reactions without necessarily providing additional benefits.