Shelf Life of Bath Products: Rancidity vs. Mold
Just like food, bath and beauty ingredients have a recommended shelf life. That refers to the length of time that a product can be stored before it becomes unfit for use. If you make your own bath products, it’s important to understand shelf life to ensure your products are safe for use. This is particularly important if you give away or sell your products.
Before we talk about shelf life, it’s important to understand the difference between rancidity and mold and bacteria growth. Rancidity and mold/bacteria growth in bath and beauty products are independent issues. Mold and bacteria can occur in products that contain water, such as lotion or emulsified scrubs. These products require a preservative to help prevent mold and bacteria growth. Click here to learn more about preservatives. They won't protect fresh ingredients (purees, fresh herbs, etc.) from growing mold in products like lotion, balms, and melt and pour soap. The pH level of cold process soap does not allow mold to grow, so you can use fresh ingredients - learn more about that here.
Rancidity is the deterioration of oils and fats. There are several types of rancidity, including oxidative rancidity, auto-oxidation, hydrolytic rancidity, and microbial rancidity. Susan Barclay-Nichols of Swift Crafty Monkey has a great blog post on rancidity here. Rancidity is a sign of an ingredient that is past its shelf life, while mold and bacteria can occur at any time.
If your product contains a preservative, the product won't grow mold/bacteria but the ingredients can still go rancid. On the flip side, mold and bacteria can grow without any rancid ingredients if the product contains water. For example, let’s say you made a lotion using excellent manufacturing practices and included a preservative. It should not grow mold or bacteria. But, the lotion also contains hazelnut oil, which has 3-month shelf life. After that time, your lotion may start to change color or smell unpleasant.
Many products and ingredients are not necessarily “unsafe” to use past their shelf life. But, rancid ingredients may smell, change color, or lose effectiveness. If you notice any of those changes, we recommended throwing it away to be on the safe side. This is particularly true for leave-on products such as lotion, or products used around the eye or lip area, like eye shadows or lip balms. If your product starts growing mold, throw it away immediately. It is unsafe for use.
Figuring out the shelf life of various products can be a little tricky. It varies depending on the type of product and the individual recipe. Some ingredients, such as fragrance oils and colorants, have an extremely long shelf life. Others, like certain fixed oils (ex: hazelnut oil, walnut oil), may have a shelf life of several months. Once you combine ingredients into one product, the shelf life of the product becomes the same as the ingredient with the shortest shelf life.
For example, let’s take a look at the Oat Oil Cleanser. Each oil has a slightly different shelf life. Castor oil has a shelf life of approximately 1 year, hemp seed oil has a shelf life of approximately 2 years, sunflower oil has a shelf life of approximately 3-6 months, and hazelnut oil has a shelf life of approximately 3 months. That means the shelf life is 3 months.
Oat Oil Cleanser for Oily Skin (shelf life of 3 months)
4 oz. Sunflower Oil (3-6 months)
2 oz. Castor Oil (1 year)
2 oz. Hazelnut Fixed Oil (3 months)
1 oz. Natural Hemp Seed Oil (2 years)
5 mL Oat Extract
2 mL Vitamin E Oil
When it comes to cold process soap, a great indicator of rancid oils are “dreaded orange spots," also known as DOS. They can occur months or years after the soap has been made. They usually appear on the corners of bars, but can also occur in the center. Several factors increase the likelihood of dreaded orange spots, but the most common is rancid oils. Find a list of oil shelf lives here. Vitamin E oil can be used to help extend the shelf life of oils, although it’s hard to say exactly how much longer it will make them last.
Soap with dreaded orange spots is still safe to use, but it usually smells quite unpleasant. The pH level of cold process soap does not allow mold or bacteria to grow. Because of this, the shelf life of cold process soap is essentially when the bars develop DOS.
Another unique example of shelf life is bath bombs. They're made by combining citric acid and baking soda. Over time, citric acid loses its potency if it's exposed to air. We recommend storing bath bombs in an airtight container in a cool, dry place and using them within 6 months for the best results.
Keep in mind that shelf lives are an estimate. Other factors, like how products are stored, also affect the shelf life. We recommend storing ingredients and products in a cool, dry place for the best results.