Guidance on Formulating a Lactic Acid and Urea Body Cream

Hello! I understand you're looking to create a body cream with a thicker texture than lotion, specifically using Lactic Acid and Urea to address dry, flaky skin, and also aiming for skin brightening. You have several detailed questions about concentrations, pH, moisturizing ingredients, and other potential additives.

Based on your questions and the provided conversation history, here is a summary and guidance:

Lactic Acid Concentration

You can use Lactic Acid 88%. If you aim for 5% active Lactic Acid in your formula (which is a recommended starting point for beginners), you would use 5.7% of the 88% concentration (calculated as 5 / 0.88 ≈ 5.68%). Using Lactic Acid at a concentration equivalent to 10% of 100% Lactic Acid might be too high for daily body use, especially initially, and would definitely require careful pH adjustment. It's best to start at 5% and gradually increase the concentration in the future if your skin tolerates it and you desire stronger results.

Daytime Application

Applying a cream containing Lactic Acid during the day is generally acceptable, but it is crucial to adjust the pH of the cream to a range suitable for the skin, typically 4.5-5.5, to minimize irritation. You should also always use sunscreen concurrently, as AHAs like Lactic Acid can make your skin more sensitive to sun exposure.

Skin Lightening Effect

Lactic Acid has exfoliating properties, which can help fade dark spots and improve overall skin tone, potentially leading to a more radiant appearance. However, the degree of whitening/brightening varies from person to person, and Lactic Acid is not primarily a skin tone altering agent like some other whitening ingredients.

pH Adjustment

The optimal pH for Lactic Acid effectiveness and skin tolerance is generally between 3.5 and 5.5. If you use a high concentration of Lactic Acid, the pH may be too low, requiring the addition of a base (alkali) like Triethanolamine or Sodium Hydroxide to raise the pH to a safe and suitable range for the skin. The exact amount of pH adjuster needed depends on the entire formula, so a specific percentage cannot be given without testing; you'll need to add it gradually while measuring the pH. An easier alternative mentioned is using Sodium Lactate, which is a neutralized form of Lactic Acid, simplifying pH control in the formula.

Moisture and Other Ingredients

• Does Lactic Acid cause dryness: You don't need to worry about Lactic Acid causing dryness. Lactic Acid is a humectant, meaning it helps attract and retain moisture in the skin.
• Urea: Adding 3% Urea should not make the cream too sticky. Urea at 5% is also recommended and is not sticky; it provides significant moisture and helps exfoliate dry, flaky skin, working well in combination with Lactic Acid.
• Cetyl Alcohol: Helps increase the viscosity of the cream, making it thicker. It also acts as an emollient, forming a protective layer on the skin to reduce water loss and provide moisture.
• Glycerin: A highly effective humectant that significantly boosts skin hydration. It can be included at 5-10% depending on your needs.
• Silicone: Improves the texture and spreadability of the cream, providing a soft, smooth, non-sticky feel. Various types are available depending on the desired finish, such as Silicone Gel (Ultra Clear, Super Silky) that provides a smooth, non-greasy feel.

Additional Brightening Agents

If you want to enhance the brightening effect, adding Niacinamide (Vitamin B3) is recommended. It's a suitable and cost-effective option for body care compared to Alpha Arbutin, which is significantly more expensive. Niacinamide at 4% (as in the sample formulas) helps with brightening, reduces redness/dark spots, strengthens the skin barrier, and adds moisture. Although Niacinamide is typically most stable in the pH range of 4-7, it can be formulated alongside Lactic Acid, possibly with careful pH control. Some forms of Vitamin C are stable at low pH but can be irritating, especially when combined with Lactic Acid. Niacinamide is generally a gentler and more versatile option in this formulation context and is a more reliable ingredient for dedicated brightening than Lactic Acid alone, although Lactic Acid contributes through exfoliation.

Shea Butter

Adding 1% Shea Butter to a formula that already contains a good amount of oil will contribute to the cream's emollience and skin-softening properties. It will also add a slight richness to the texture. The overall impact on viscosity at 1% might be minor depending on the base formula, but it will definitely improve the feel on the skin.

Sample Formulas (Based on Provided Information)

Here are sample formulas you can use as a starting point:

Gel Base Formula

• Xanthan Gum (Thickener): 0.5-1% (adjust for desired viscosity)
• Lactic Acid (88% concentration): 5.7% (equivalent to 5% active Lactic Acid)
• Urea: 5%
• Niacinamide (Vitamin B3): 4%
• Glycerin: 5-10%
• Distilled Water: Remaining percentage
• Adjust pH to not lower than 3.5

Lotion Base Formula (with oil)

• Light Cream Maker (Emulsifier): 1.5%
• Natural Oil (e.g., Olive Oil): 10%
• Lactic Acid (88% concentration): 5.7% (equivalent to 5% active Lactic Acid)
• Urea: 5%
• Niacinamide (Vitamin B3): 4%
• Glycerin: 5-10%
• Distilled Water: Remaining percentage
• Adjust pH to not lower than 3.5

It's recommended to start by making a small batch and testing it on a small area of your skin to see how it responds. If you plan to use higher concentrations of Lactic Acid, using a pH meter to accurately control the pH is highly recommended for safety and optimal effectiveness.