In the great tradition of advice columnists like Miss Manners and Dear Abby, Miss Micro will attempt to answer your most pressing questions about product preservation. The views expressed here are based on the extensive experience and exhaustive research by Miss Micro. Your anonymous questions for Miss Micro can be addressed to [email protected].



Dear Miss Micro,

What’s your opinion of rapid micro-check test methods by QC: 1) prior to product release for revenue sale, 2) for surface swabs taken on manufacturing equipment before batch making and 3) for process water?
-Tired of Waiting (Seattle, WA)

Dear Tired,

Rapid methods are widely used in the foods industry. They are very effective if you need to know the bio-burden of something at a specific point in time. The equipment is expensive and the methods must be validated relative to the specific use. The faster and more sensitive the equipment, the more it costs. Typically, a microbial load of 10 log3 is needed for these rapid methods to show a positive reading. Lower levels of contamination can be read if an enrichment step is used first. Results can be available immediately or up to 24 hours, depending on the method. This compares to traditional plate counts that can read less than 10 log3 with or without enrichment, but need 48-72 hours or longer for colonies to be read.

If you can afford rapid micro methods equipment and can validate it properly, then this is a great way to clear product for release, equipment for use, and water for manufacturing. However, these are not methods for the novice. Validation is extremely important. These methods are also not a substitute for preservative efficacy testing (PET). Even a sterile product, manufactured aseptically can be easily contaminated in the hands of the consumer. Only PET testing can assure that the product is safe for consumer use.



Dear Miss Micro,

Our company manufactured a batch of product and the lab shows that it is microbiologically contaminated. What preservative can we add to the batch to clean it up? Or maybe we can irradiate it?
-Panicked (Pasadena, CA)

Dear Panicked,

My suggestion is to discard the batch, check your plant and materials for contamination and start again. Preservatives are used to protect a product from inadvertent contamination from manufacturing or consumer usage. They should never be used to try to decontaminate a contaminated batch of product. Preservatives are designed to kill living cells. At too high a level, they will begin to pose a health risk to the consumer. It is always best to make certain that you are working with microbiologically sound raw materials and that your equipment is clean and properly sanitized before you start a batch. Also, finished formulations should always be challenge tested before they go into production. Just because you made something similar before with a certain preservative system doesn’t mean that the next formulation will be adequately preserved with the same system. Something as minor as changing the fragrance may have a major impact on the preservative efficacy, since some fragrance compounds have preservative effect.

I also don’t like the idea of irradiating a contaminated consumer product. All that leaves you with is an inadequately preserved product with a lot of tiny dead bodies floating around in it. Dead microorganisms can release toxins that can impact the consumer. Best to take the loss and start again clean.



Dear Miss Micro,

I try to treat my body well. I exercise, eat fresh, minimally processed food and try to avoid preservatives when possible. Should I be worried about the preservatives in my cosmetics also?
-Earth Crunchy (Provo, UT)

Dear Earthy,

While I applaud your efforts to maintain your health and wellbeing, the main problem with processed foods is not the preservatives, but the added salt, sugar and fat that your body probably doesn’t need. Much like the fresh food that you eat, cosmetics are a great place for microorganisms to grow. Without an effective preservative system, cosmetics would have to be packaged for single use (expensive!), packaged in airtight containers, and/or kept in your refrigerator and discarded after a short time like your fresh foods. Think of how inconvenient it would be to have to retrieve your shampoo from the refrigerator each morning.

Any cosmetic product containing water requires the addition of an effective preservative system as protection against microbial contamination over the full life of the product. Without this protection, there is the risk of contamination that can cause infection or, at minimum, make your product look and smell bad. Most cosmetic preservatives currently in use have been extensively tested and found extremely safe to use at their recommended level. In comparison, the health risk from a contaminated cosmetic is significant.



Dear Miss Micro,

Formaledhyde makes me think of dissecting frogs in junior high school. It smells bad and I have read that it may cause cancer. Why is it used to preserve cosmetics?
-Fromaldehyde-free (Boulder, CO)

Dear Formaldehyde-Free,

Formaldehyde is rarely used to preserve cosmetics in North America. What is used are chemicals often classified as “Formaldehyde-donors”. They are classified this way because the destructive testing used to analyze for their presence produces an aldehyde that looks like formaldehyde in the testing. In actuality, what they produce in product is methylene glycol, the aqueous form of formaldehyde gas. This is a minor, but important, distinction. Formaldehyde gas had been found to be carcinogenic by inhalation. Methylene glycol had been found to be non-carcinogenic. “Formaldehyde-donor” chemistry is among the safest, most effective, and most cost-effective preservatives on the market today.



Dear Miss Micro,

I have heard that parabens used in cosmetics cause breast cancer. Should I see my doctor?
-Worried (Santa Monica, CA)

Dear Worried,

You may want to see your doctor, but not because of parabens in your cosmetics. There have been several studies investigating the estrogenic effect of parabens. Most of them have significant flaws and none of them found a causal link between parabens and cancer. While testing has shown parabens to be estrogenic, that effect is 10,000 to 2,500,000 times less than estrogen. In comparison, soy is known to be a phytoestrogen (plant version of estrogen). Countries where soy protein is widely consumed are also the countries with some of the lowest incidence of breast cancer in the world.

What you may be more concerned about is infections caused by inadequately preserved or shared cosmetics. Inadequately preserved personal care products can harbor microbial contamination. If this contamination is introduced to a cut or your eye, it can result in a serious infection, requiring medical attention.