PRESERVATIVES

What are preservatives used for?

Preservatives are used to keep a product shelf stable for a longer period of time than it

would by itself. They are also put in products to prevent the growth of harmful molds, fungi, and

bacteria that would occur without them. However, food is not the only thing that needs

preservatives. Cosmetic products need preservatives too! Without them, bacteria would be

transferred from the skin back into the container via application brushes or the fingers, where it

could multiply unobstructed. One seemingly obvious solution is to just make products that are

extremely acidic or extremely alkaline (basic) to prevent bacterial growth, but this would result

in damage to the skin, which is very sensitive to pH changes.

What kinds of preservatives are there?

There are many different kinds of preservatives. These include aldehydes, glycol ethers,

isothiazolinones, organic acids, and parabens.

Aldehydes are carbon-based compounds that contain an aldehyde group (a carbon

double-bonded to oxygen and single-bonded to a hydrogen). This group includes formaldehyde,

which is notorious for the smell it produces in laboratories and hospitals, and formaldehyde

producing compounds. They are very effective antimicrobials as they react with proteins and

peptides, destroying them and preventing the bacteria from replicating. However, formaldehydes

and products that decompose into formaldehyde are extremely dangerous to human health.

Glycol ethers are a group of ethers that have a glycol base and an ether functional group.

They include phenoxyethanol and caprylyl glycol. A glycol is an alcohol with two hydroxyl

groups, also known as a diol. An ether functional group is a carbon with a hydroxyl group and an

oxygen double bonded to it. They are soluble in oils and water. They are very effective againstgram-negative bacteria. While they are not broad-spectrum, they are considered a milder and less

irritating alternative to other preservatives.

Isothiazolinones are five-sided rings, one side of which has a carbon/carbon double bond.

One point on the ring is a sulfur, another is a nitrogen, and one carbon that is double-bonded to

oxygen. They are broad-spectrum preservatives and have the bonus of being effective in the full

range of pH values.

Organic acids are simply organic or carbon based compounds with acidic properties.

These include acetic acid, lactic acid, anisic acid, and benzoic acid as well as the sorbates. They

are sometimes considered natural despite being created synthetically. In products with high water

content, they precipitate out and lose their effectiveness. While they are strong against fungi,

they do not have much of an effect against bacteria.

Parabens are a form of hydroxybenzoate attached to an alkyl (chain of single-bonded

carbons) group. They have bactericidal and fungicidal properties and are used in foods,

cosmetics, and pharmaceuticals. These are the most common preservatives found in cosmetics.

They are permitted for use in leave on and rinse off products. However, there is also a

controversy over their effects on human health.

Parfum is not a single compound but a mixture of dozens of them. It is a broad spectrum

preservative that is soluble in water, alcohols, and glycols. While it smells nice, it is very

expensive.

Some antioxidants are often touted as preservatives. While they have less intimidating

and more ‘natural’ names, they will not accomplish the job. These are sodium lactate, grapefruit

seed extract, rosemary antioxidant, and vitamin E.

What are some preservatives in each of these categories?The aldehydes include Germall Plus, DMDM, Imidazolidinyl Urea, and Diazolidinyl

Urea. The glycol ethers include phenoxyethanol, Optiphen, and Optiphen II. Isothiazolones

include Kathon. Organic acids include Geogard, Neodefend, Euxyl, sodium benzoate, potassium

sorbate, anisic acid, and levulinic acid. Parabens include Germaben II, Methylparaben,

Propylparben, and Butylparben, and Pheonip.

Are they safe?

The FDA does not have any regulations for cosmetic products. Instead, it is the burden of

the manufacturer to ensure that the ingredients are safe. However, there are laws that require

product labels to show what they contain.

Parabens are one of the most controversial of the preservatives. They are notorious for

mimicking estrogens. In large amounts, they may disrupt hormone function, giving them the title

of an ‘endocrine disruptor.’ This has led many companies to seek alternatives to parabens in their

products.

One alternative that has been tried is phenoxyethanol. However, it has its own health

concerns. It has the potential to cause an allergic reaction. Ingestion of phenoxyethanol can result

in vomiting, diarrhea, and respiratory irritation.

Formaldehydes and preservatives that decompose into formaldehyde are hazardous to

human health. It is a known carcinogen and can also cause contact dermatitis, even in short term

use. Quaternium 15, a common preservative in many cosmetics, decomposes into amounts of

formaldehyde that are small enough to be considered safe. However, this has not shown to be

beneficial in any way. Many cosmetics companies are phasing out this dangerous class of

preservatives.Do I need preservatives in my DIY skincare?

Preservatives are not required in any homemade products. However, if you plan to sell

them, some kind of preservative should be included to prevent spoilage. If you do not add a

preservative to your formulation, treat it as you would a fresh fruit or vegetable by putting it in a

refrigerator to prevent fungi and bacteria growth. Products that are not water based do not

normally need preservatives.

How much of X preservative do I need?

This varies based on the product and the preservative. Typical usage rates are .5% to

2.5% by mass. If you have 100g of other ingredients, then 1% usage rate means you add one

gram to the mixture.

Which preservative should I use?

There are too many preservatives to choose from, but no table or website can tell you

which one to use. Instead, do your own research. Take into account the product you’re putting it

in. Is it oil based? Water based? What pH will it have? Are any of the other ingredients

preservatives too? Are you willing to use multiple preservatives? Is cost a factor? All of these

can change which preservative is best for your recipe.