Formulating Non-Stinging AHA + BHA Products

Thank you for your question regarding formulating an AHA + BHA product that doesn't cause a stinging sensation, similar to the Clinicians Complex Acne Toner you've used.

Based on the ingredient list you provided and general formulation principles, the reason the Clinicians Complex toner might not cause stinging could be a combination of factors:

• pH Adjustment: While you weren't able to measure the pH, the presence of a pH adjuster like Triethanolamine suggests the formula's pH might have been raised. As the staff mentioned regarding Glycolic Acid, increasing the pH significantly reduces the amount of free acid available, thus lowering its efficacy but also reducing irritation.
• Soothing Ingredients: The formula contains ingredients like Witch Hazel and Chamomilla Extract. These botanical extracts are known for their soothing and anti-inflammatory properties, which can help counteract the irritation caused by acids.

Regarding the efficacy of AHA and BHA at a higher pH (like 5.5+), as indicated by the information on Glycolic Acid, the effectiveness of these acids is highly dependent on pH. At pH levels significantly higher than their pKa (around 3.0-4.0 for AHAs and BHA), a much smaller percentage of the acid is in its active, un-ionized form. This means that while a higher pH reduces stinging, it also substantially reduces the exfoliating and pore-clearing efficacy of ingredients like Glycolic Acid, Lactic Acid, Malic Acid, Citric Acid, and Salicylic Acid.

If you wish to formulate an AHA + BHA product that minimizes stinging, you have two primary approaches, each with trade-offs:

1. Increase the pH: Raising the pH (e.g., towards 4.0-5.0 or even higher) using a pH adjuster like Triethanolamine will definitely reduce or eliminate the stinging sensation. However, be aware that this will also significantly decrease the efficacy of the AHA and BHA components. This approach prioritizes comfort over maximum exfoliation power.

2. Incorporate Soothing and Barrier-Supporting Ingredients: You can formulate your product at a more optimal pH for AHA/BHA efficacy (typically pH 3.0-4.0) and add ingredients specifically designed to reduce irritation and support the skin barrier. Examples include:

   • Soothing Agents: Ingredients like FastRelief™, Natural Bisabolol (derived from Chamomile), Witch Hazel, and Chamomile Water can help calm the skin and reduce the perception of stinging.
   • Humectants and Barrier Support: Ingredients like Propylene Glycol and Urea, which were present in the Clinicians Complex toner, can help hydrate the skin and support its natural barrier function, making it less prone to irritation.

Choosing the right approach depends on your priority: maximum efficacy (requiring a lower pH and potentially needing soothing agents) or maximum comfort (achieved by a higher pH, but with reduced efficacy).

Key ingredients to consider for your formulation include Salicylic Acid, Glycolic Acid, Lactic Acid, Malic Acid, Citric Acid, Witch Hazel, Chamomile Extract/Water, Natural Bisabolol, FastRelief™, Triethanolamine (for pH adjustment), Propylene Glycol, and Urea. You can also continue using Retinaldehyde as part of your overall routine for managing acne and clogged pores.