If you are formulating something that contains fluids like water, milk, and even hydrosols, you will have to preserve the product in some way, or store it in the refrigerator and use within 3-4 days.

So what “natural” preservatives can you use to extend the life of your homemade product?

Natural product manufacturers have used essential oils to preserve their products and so can you.

Many studies have demonstrated essential oils to have both antimicrobial and antioxidant activity.

The percentage of essential oil required to adequately protect a product from microbial growth and oxidation usually exceeds the recommendations for safe amounts of essential oils to use in skin care products.

However, high concentration of essential oil can be used in aromatic room sprays. 

If the only ingredient in your water-based product is pure essential oils then no preservative "may" be required to maintain freshness. Although, because water is considered a breeding ground for bacteria some experts still recommend you use a preservative even when using high concentrations of essential oil.

Its common to see recipes for DIY aromatherapy sprays to use water alone with essential oils. Also, a few well known aromatherapy manufacturers offer “preservative-free” spray formulations with only pure water and possibly one other additional ingredient such as witch hazel (which acts as a preservative) with instructions to shake well and spray before using.

You just need to remember that what you make at home will have a shorter shelf life, especially when it contains fluid substances like water. 

Natural Preservatives - Ghostbusters!!

Antioxidants 

An anti-oxidant acts to slow down the rate of oxidation of your oils and help preserve your product. A product that has oxidized gives off a very rancid aroma and can turn brown in color. Antioxidants prevent rancidity and discoloration from occurring, but do not kill microbes. 

Anti-Microbials

An anti-microbial helps to inhibit harmful micro-organisms like bacteria from growing in your homemade goodies. As well as, help preserve a product’s freshness and keep it free of unwanted micro-organisms

Although not as long-lasting as store-bought products with chemical preservatives these “natural alternatives” will extend the shelf life of your DIY products when properly used.

• Essential oil (i.e. rosemary, eucalyptus, peppermint, lavender, lemongrass, oregano, thyme, clove, cinnamon, bergamot, basil, tea tree)
• Vitamin E (organic, Non-GMO source)
• Citric or ascorbic acid (Certified organic Non-GMO). Citric and ascorbic acid are corn based derivatives and may contain GMOs. Be sure to buy organic or GMO certified free.
• Alcohol (isopropyl or spirits, i.e. Everclear which is 95% ethanol is best)
• Grapefruit seed extract (Organic citricidals - a class of antimicrobials). Studies show the commercial GSE product has potential to be contaminated with benzalkonium chloride, parabens, and triclosan. Be sure to buy organic.
• Witch hazel (Hamamelis Virginiana)
• Vinegar 
• Salt 
• Sugar

READ first article in this series, Traditional "Artisan" Methods Preservative-Free Custom Formulations.