Preservative Selection for Homemade Cosmetics

For your formulations, particularly lotions and liquid soaps which contain water, it is essential to use a preservative to prevent the growth of microorganisms such as bacteria, mold, and yeast. This growth can spoil the product and potentially cause harm to the skin.

For oil-based formulas, such as your second example with almond oil, coconut oil, beeswax, shea butter, and Vit E oil, traditional preservatives are generally not required as they lack the water activity needed for most microbes to thrive. However, adding Vitamin E oil to oil-based formulas is beneficial as it acts as an antioxidant, helping to prevent the oils from going rancid.

Based on your query and the previous reply, here are some relevant preservatives for water-based formulations:

• Mild Preserved Group:
  • Mild Preserved Eco™ and Mild Preserved SC10™ typically combine Ethylhexylglycerin with other ingredients (like Propanediol or Caprylyl Glycol). Their advantages include being gentle, non-irritating, and potentially allowing a "Preservative-Free" claim in some regions as they may not be classified strictly as preservatives by regulatory bodies. They also offer humectant properties. They are effective over a relatively wide pH range and have good short-term heat tolerance. They are suitable for general formulations where mildness is desired.
• Group Phenoxyethanol:
  • Phenoxyethanol (Extra Pure) is a safe preservative, free from Parabens and Formaldehyde, which are considered potential carcinogens. The Extra Pure grade has higher purity, reducing the risk of skin irritation compared to standard grades. However, Phenoxyethanol alone may not be fully effective against fungi, so it might need to be combined with other preservatives or a broad-spectrum blend should be chosen instead.
  • Phenoxyethanol SA (eq. Optiphen Plus) is a broad-spectrum preservative blend containing Phenoxyethanol, Caprylyl Glycol, and Sorbic Acid. This combination provides better efficacy against both bacteria and fungi. It may also allow for a lower concentration of Phenoxyethanol, potentially leading to less irritation than using Phenoxyethanol alone. It is suitable for various product types but has limitations regarding optimal pH range (around 2.0-6.0) and mixing temperature (below 60°C).
• Eye Preserved™ (Polyhexamethylene Biguanide, PHMB):
  • This preservative was developed for use in contact lens solutions and is known for its gentleness, making it suitable for products used around the eyes or for sensitive skin. It is an effective disinfectant and has high heat resistance. However, a key consideration is its incompatibility with many anionic thickeners or gelling agents (like Carbomer or Xanthan Gum). Its efficacy against pathogens might be lower than some other preservative groups, so if used as the sole primary preservative, strict manufacturing hygiene is crucial, or it should be combined with other preservatives. It works best in a pH range of 3-8 (ideally 3-6.5).
• NaturePreserve™ Group:
  • NaturePreserve™ Ultra (Gluconolactone & Sodium Benzoate) and NaturePreserve™ LB2 (Dehydroacetic Acid & Benzoic Acid & Benzyl Alcohol) are preservatives derived from natural sources, suitable for those seeking high natural content in their products. They are effective against microbes but have specific pH range requirements for optimal function (NaturePreserve™ Ultra at pH 3-6, NaturePreserve™ LB2 at pH 2.0-6.5). NaturePreserve™ LB2 should also avoid temperatures above 50°C.

Summary and Recommendation:

For your lotion and liquid soap formulas, aiming for high safety and mildness:

1. Mild Preserved Group (Eco or SC10): A good choice if you desire a "Preservative-Free" claim and high mildness. They are generally easy to incorporate into standard formulations.
2. Phenoxyethanol SA: A safe and effective broad-spectrum option (covering a wide range of microbes). It's suitable for formulas requiring robust preservation and has a lower potential for irritation compared to using Phenoxyethanol by itself.
3. NaturePreserve™ (Ultra or LB2): An alternative for formulas emphasizing natural ingredients. You must ensure your formula's pH falls within the effective range for these preservatives.

Choosing the "safest" preservative depends on the specifics of your formula, including other ingredients, the final product's pH, and any desired claims (e.g., "preservative-free", "natural"). The preservatives mentioned above are commonly used in cosmetics and are considered safe when used correctly within recommended guidelines.

Crucially, performing a Challenge Test on your final product formula is highly recommended to confirm that the chosen preservative system, at your chosen concentration, effectively protects against microbial growth throughout the product's intended shelf life, especially if you plan to sell your products.

For your oil-based formula (almond oil + coconut oil + beeswax + shea butter + Vit E oil), a traditional preservative is not typically needed. The Vitamin E oil in your formula already serves as an antioxidant to help prevent the oils from becoming rancid.