Tuesday, October 16, 2018
If your product contains water then you will normally need a preservative to prevent the growth of harmful bacteria and microbes. In the UK and the EU before a product containing water can be sold or given away the formula must undergo preservative efficacy testing to ensure that the preservative is effective under various conditions.
Products containing a small percentage of water and high percentage of glycerin or sugar may be able to avoid the need for a preservative. I use a preservative in all of my leave in products that contain water. However, if I'm making a small batch of conditioner or shampoo that will be rinsed out there isn't any need for a preservative. Anhydrous products such a oils, butters and pomades do not require a preservative but you may need an antioxidant such as Vitamin E to prevent the oils from going rancid. You will also need an antioxidant if you use essential oils in your formula.
A friend of mine recently told me that she had been making her own products using recipes from YouTube. She told me she was using aloe vera mixed with water and a few essential oils. I questioned her on the use of a preservative and she said that she keeps the product in the fridge. I explained that refrigeration only protects the product while it's in the fridge but if you apply the product to your hair and leave it on for more than 24 hours the bacteria would have adequate opportunity to multiply on your head. She asked about adding water or aloe vera to store bought products that already contain preservatives. I explained that preservatives are normally used at approximately 1% of the formula, if you add other ingredients to the formula you are reducing the percentage of preservative and it may no longer be as effective.
The bottom line is, if you make your own products containing water, rinse them off within a few hours or use a preservative.