Valerie George08.01.23
Dear Valerie:
I’m working on a two-in-one self-tanner for a customer using DHA and erythrulose. It exfoliates the skin at the same time it tans skin. Any tips?
—Brown ’n Peel
Dear Brown:
As cosmetic chemists, we generally create formulas that don’t react on the skin or hair. Exceptions include hair colorants and lighteners, perms and self-tanners. You want these to react when used by the consumer. However, you don’t want anything happening in the bottle. This is where formulating reactive products is challenging, especially with dihydroxyacetone, one of the original self-tanning ingredients on the market.
Fortunately, DHA is a reactive ingredient which imparts beautiful tans. They can be made more beautiful (and less orange-you-glad-I-didn’t-say-banana) with the addition of erythrulose. On the flip side, DHA is a reactive ingredient and can react in the bottle before a consumer has a chance to use it. It is extremely reactive and is quickly prone to oxidation. Therefore, the trick to formulating a successful DHA-based self-tanner is to use as few ingredients as possible. Additionally, you must watch what other ingredients you do use.
You can’t use anything with nitrogen groups; they will prematurely react with the DHA or metals, which promote oxidation. Another group to avoid is phosphates, as DHA is famous for pH downward drift—don’t try to fight it with a buffer system! Exfoliating acids degrade DHA, so I’m not sure how you intend to achieve a simultaneous exfoliating effect. Also use caution with your preservation system, as DHA is most stable with preservatives like parabens.
You can help fight the oxidation by adding antioxidants like sodium sulfite, and keeping DHA in its happy place with a formulation pH around 4.
Dear Valerie:
Is it possible to use salicylic acid in an anhydrous formulation or does it have to be in an aqueous formula? I’m curious because I know it’s oil soluble, but I thought acids need a low pH to be effective.
—Proper pH
Dear Proper:
I don’t believe water is a requirement to aid in penetration of salicylic acid into the stratum corneum, so I would not be concerned from this perspective. Lipids love skin, or is it skin loves lipids? If salicylic acid is in an anhydrous serum, it should be able to interact with and penetrate the skin. This is especially true if it were coupled with a penetration enhancer like dimethyl isosorbide.
Now onto the factor of pH. While your formulation may not have a pH, the salicylic acid will interact with the pH of your skin and theoretically generate a pH as it penetrates. This should suffice for salicylic acid to have some activity. Now how low the pH goes, I’m not sure. This actually might not be too important because a 2008 study evaluated the ability of salicylic acid to exfoliate at a pH of 6.5 versus a pH of 3.12 and found they both exerted the same desquamatory effects after two days.1 I would therefore wager that whatever the pH is of your skin isn’t important, because salicylic acid will still have the same effects. Not to mention, you could create more gentle formulas utilizing a neutral pH.
I also want to note that salicylic acid does have other benefits that are not tied to its pH or corneodesmolytic properties. For example, a 2019 study proposed a possible mechanism of salicylic acid to downregulate sebum production and act as an anti-inflammatory agent via cytokine suppression for sebocytes, which was validated in vitro and in vivo on a rabbit’s ear.2
I hope this helped! I wouldn’t worry so much about pH but delivering salicylic acid to the skin and enjoying its efficacy.
Dear Valerie:
I made a shampoo using Ammonium Laureth Sulfate, Cocamidopropyl Hydroxysultaine, EGDS and Cocamide MEA. I’m getting a large portion of separation at the bottom after a short period of time. I’ve used EGDS before so I’m not sure what could be going wrong. My pH is 5.0, viscosity around 2,000cps.
—Separation Anxiety
Dear Separation:
From an ingredient perspective, everything looks good. However, I think the shampoo, even excluding your separation issues, is too thin to sustain Cocamide MEA and EGDS. These crystalize back into a tight network that looks like little platelets. These need to remain suspended in your system. Unfortunately, at 2,000cps (which seems quite low for a formulation like this, anyway!), you won’t get the yield you need to support the pearlescence.
Consider improving your viscosity with more salt, altering your surfactant ratios, increasing your overall surfactant load, or adding a thickener like hydroxypropyl methylcellulose or a polymer suitable for shampoo systems to bolster your viscosity. I think you’ll see dramatic results when you can suspend your pearlescence.
References
Valerie George
[email protected]
Valerie George is a cosmetic chemist, science communicator, educator, leader, and avid proponent of transparency in the beauty industry. She works on the latest research in hair color and hair care at her company, Simply Formulas, and is the co-host of The Beauty Brains podcast. You can find her on Instagram at @cosmetic_chemist or showcasing her favorite ingredients to small brands and home formulators at simply-ingredients.com
I’m working on a two-in-one self-tanner for a customer using DHA and erythrulose. It exfoliates the skin at the same time it tans skin. Any tips?
—Brown ’n Peel
Dear Brown:
As cosmetic chemists, we generally create formulas that don’t react on the skin or hair. Exceptions include hair colorants and lighteners, perms and self-tanners. You want these to react when used by the consumer. However, you don’t want anything happening in the bottle. This is where formulating reactive products is challenging, especially with dihydroxyacetone, one of the original self-tanning ingredients on the market.
Fortunately, DHA is a reactive ingredient which imparts beautiful tans. They can be made more beautiful (and less orange-you-glad-I-didn’t-say-banana) with the addition of erythrulose. On the flip side, DHA is a reactive ingredient and can react in the bottle before a consumer has a chance to use it. It is extremely reactive and is quickly prone to oxidation. Therefore, the trick to formulating a successful DHA-based self-tanner is to use as few ingredients as possible. Additionally, you must watch what other ingredients you do use.
You can’t use anything with nitrogen groups; they will prematurely react with the DHA or metals, which promote oxidation. Another group to avoid is phosphates, as DHA is famous for pH downward drift—don’t try to fight it with a buffer system! Exfoliating acids degrade DHA, so I’m not sure how you intend to achieve a simultaneous exfoliating effect. Also use caution with your preservation system, as DHA is most stable with preservatives like parabens.
You can help fight the oxidation by adding antioxidants like sodium sulfite, and keeping DHA in its happy place with a formulation pH around 4.
Dear Valerie:
Is it possible to use salicylic acid in an anhydrous formulation or does it have to be in an aqueous formula? I’m curious because I know it’s oil soluble, but I thought acids need a low pH to be effective.
—Proper pH
Dear Proper:
I don’t believe water is a requirement to aid in penetration of salicylic acid into the stratum corneum, so I would not be concerned from this perspective. Lipids love skin, or is it skin loves lipids? If salicylic acid is in an anhydrous serum, it should be able to interact with and penetrate the skin. This is especially true if it were coupled with a penetration enhancer like dimethyl isosorbide.
Now onto the factor of pH. While your formulation may not have a pH, the salicylic acid will interact with the pH of your skin and theoretically generate a pH as it penetrates. This should suffice for salicylic acid to have some activity. Now how low the pH goes, I’m not sure. This actually might not be too important because a 2008 study evaluated the ability of salicylic acid to exfoliate at a pH of 6.5 versus a pH of 3.12 and found they both exerted the same desquamatory effects after two days.1 I would therefore wager that whatever the pH is of your skin isn’t important, because salicylic acid will still have the same effects. Not to mention, you could create more gentle formulas utilizing a neutral pH.
I also want to note that salicylic acid does have other benefits that are not tied to its pH or corneodesmolytic properties. For example, a 2019 study proposed a possible mechanism of salicylic acid to downregulate sebum production and act as an anti-inflammatory agent via cytokine suppression for sebocytes, which was validated in vitro and in vivo on a rabbit’s ear.2
I hope this helped! I wouldn’t worry so much about pH but delivering salicylic acid to the skin and enjoying its efficacy.
Dear Valerie:
I made a shampoo using Ammonium Laureth Sulfate, Cocamidopropyl Hydroxysultaine, EGDS and Cocamide MEA. I’m getting a large portion of separation at the bottom after a short period of time. I’ve used EGDS before so I’m not sure what could be going wrong. My pH is 5.0, viscosity around 2,000cps.
—Separation Anxiety
Dear Separation:
From an ingredient perspective, everything looks good. However, I think the shampoo, even excluding your separation issues, is too thin to sustain Cocamide MEA and EGDS. These crystalize back into a tight network that looks like little platelets. These need to remain suspended in your system. Unfortunately, at 2,000cps (which seems quite low for a formulation like this, anyway!), you won’t get the yield you need to support the pearlescence.
Consider improving your viscosity with more salt, altering your surfactant ratios, increasing your overall surfactant load, or adding a thickener like hydroxypropyl methylcellulose or a polymer suitable for shampoo systems to bolster your viscosity. I think you’ll see dramatic results when you can suspend your pearlescence.
References
- Merinville, E.; Laloeuf, A.; Jalby, O.; Rawlings, A.V.; Morán, G. Exfoliation for sensitive skin with neutralized salicylic acid? Int. J. Cosmet. Sci. 2009, 31, 243–244.
- Lu J, Cong T, Wen X, et al. Salicylic acid treats acne vulgaris by suppressing AMPK/SREBP1 pathway in sebocytes. Exp Dermatol. 2019;28 (7):786–794. doi:10.1111/exd.13934
Valerie George
[email protected]
Valerie George is a cosmetic chemist, science communicator, educator, leader, and avid proponent of transparency in the beauty industry. She works on the latest research in hair color and hair care at her company, Simply Formulas, and is the co-host of The Beauty Brains podcast. You can find her on Instagram at @cosmetic_chemist or showcasing her favorite ingredients to small brands and home formulators at simply-ingredients.com