Wednesday, February 2, 2011

Do we need preservatives in soap?

In this post, Heidi asks...My question is this.They tell us we don't need preservatives in soaps. Do you believe this is true? And if it is, why do we need a preservative in a solid shampoo bar (syndet)?And how about something without water like a body lotion bar?

Great question! Let's take a look at bacterial contamination in soap first.

Washing hands with contaminated soap bar unlikely to transfer bacteria. This is a study from 1998 and seems to be one of the most quoted ones. In essence, the title says it all.

Microbial contamination of "in use" bar soap in dental clinics. This one showed that soaps in a dental clinic can be contaminated by microbes, but it doesn't note if those microbes are transferred to other users. This sentence caught my eye: "The Center for Disease Control -1989 chapter 8, suggests that bar soaps should not be used for hand washing." I'm hoping this is just in medical settings!

Bacteriological studies related to hand washing. The conclusions in this one are interesting (last page). In quick summary, bar soaps do not support the growth of bacteria and said bacteria couldn't be passed on from one person to another. Bar soaps are anti-bacterial by their physical and chemical nature, but even if they were contaminated, this wouldn't be passed on to someone else. But this was published in 1963, so who knows if it's still relevant information?

I'm actually quite surprised there haven't been any more large, recent studies on this topic (almost everything else I found had tiny groups - say 6 people - or was about anti-bacterial soaps). Having said that, the general consensus appears to be that soap bars may harbour some contamination, but it's not being transferred to the user. Suggestions for keeping soap from obtaining more contamination are to keep it in a well drained container and to keep it dry.

As for the rest of your question, I use preservatives in my shampoo and conditioner bars because they're usually sitting in water in the shower as the silly soap holding thing doesn't drain well (I keep meaning to buy a new one, but it's not really on the top of my to-do list!). If I put them into a bag or other container, they're still sitting there wet after usage, so I think it wiser to add a preservative than to not.

As for anhydrous products like a lotion bar, every day microbes don't want to grow in oil so it's fine to leave the preservatives out of products that don't contain water and won't be exposed to water.


melian1 said...

the quote from one study says: "The Center for Disease Control -1989 chapter 8, suggests that bar soaps should not be used for hand washing."

it seems to me that knowledge of chemistry, medical knowledge, and the study of microbiology has progressed in the past 22 years. not much of anything else in those fields is still accurate after 2 decades, i wonder why this is?

on the dr. oz show last year, there was a question about bar soap being used by multiple people. the study he quoted, tho i don't know if he ran it specifically to answer the question or if it had been done elsewhere and his researchers found it, did microbial testing of a bar of soap before use, after (iirc) 16 different men in a shower room used it, and again after it had sat overnight.

they found that there was in fact various microbes on the soap but it never passed from one person to another. their conclusion was that the soap didn't allow the microbes to get on the skin, they washed away down the drain. the conclusion was that bar soap is excellent for getting rid of the various sorts of germs that we run into, as there was none on the skin of the volunteer test subjects after using the soap.

there was mention of a study either done or intended to be done of nurses and doctors in a medical setting in that same episode, but i can't recall anything about it.

i wonder if someone contacted the show and asked if they would pull their records and give us specifics? my memory is a poor substitute for hard information!

Heidi said...

Wow! A whole post on my question.


I have been thinking about making up some salves and even though they won't have any water in them I am wondering if they would need a preservative?

One will be a baby bum salve and I'm thinking, hmmm we are rubbing it on a bum, and even without water I was wondering if a preservative would be a good idea. Your thoughts?

The other salves would be made with herbs infused into oils and I was wondering about using a preservative with this.

If I don't need one, GREAT! But it does come down to safety first.

I understand some people wanting to go as natural as possible. With all the information we hear about how cancer is wide spread and reports on the news about higher rates of autism near chemical factories I understand wanting all natural. BUT, I also understand mold being very dangerous as well. I also want to be as natural as possible, but I also want to be safe.

So what's your thoughts on the salves?


P.S. I just made a solid shampoo bar and used it once .... so far I LOVE it! Next I will be trying out the conditioner bar. Excited!

Susan Barclay-Nichols said...

Hi Melian! I was surprised to see how little information is out there on soaps that aren't considered anti-bacterial. The general consensus seems to be that although soap can get some contamination on it, that contamination isn't transferred to our hands (as you point out).

Hi Heidi! If you're in doubt, add a preservative. Something like Phenonip or Liquipar Oil are good choices for anhydrous products. We don't really need a preservative in anhydrous products, except when they might come into contact with water, but if you're worried, adding an oil soluble preservative isn't a bad idea. I'd rather be safe than sorry when it comes to my health, and I'm far more worried about microbes and bacteria with my sensitive, often broken skin than I am about a little preservative.

I'm glad you like the shampoo bar! I won't wash my hair without one! You'll love the conditioner bars, too!