What's in your shampoo? Part 2 - Parabens

Dear Readers,

Let's resume our journey through Shampoo making by looking at one ingredient that has lead manufacturers to misery and consumers to awareness: Parabens.
Note that this ingredient is present in most cosmetics, not only shampoos.
Scientific literature is R.I.C.H. with articles about Parabens and throughout my reading, I probably had doubts a few times as to their safe use. In the end, I compiled a lot of information here below and if you are concerned about them and want to really know what is it about, then - although I know it's long! - it is really worth to read it all!!! I am not your doctor nor your GP, and will not tell you if it's good or bad, if you should ban Parabens from your life or not, I think it is important that you should formulate your personal opinion. I laid out all the latest research for you to do so. I hope you find this informative. Personally, after reading it all, I know I don't need to worry anymore!

You can catch up with the first instalment of this mini-series here: Shampoo making recipe

Parabens

Structure

Parabens are a group of esters of 4-hydroxybenzoic acid only differing from one another in the ester part of the molecule (fig.1: here represented by R).

Figure 1. Paraben structure. From Soni et al, 2005

That R can be a methyl group (chemically known as -CH3), or ethyl (aka -CH2CH3), propyl (aka -CH2CH2CH3, butyl (-CH2CH2CH2CH3), etc... 

That is why when you read your labels, you can have different types of parabens like methylparaben, ethylparaben, propylparaben, etc....

The difference between them is their solubility in oil, their resistance in degradation and their anti-microbial activity.

Parabens occur naturally in foods like blueberries, yellow passion fruit, white wine or Bourbon vanilla!!

Uses

There are 3 main uses for Parabens: As a food ingredient, in cosmetics and in pharmaceutical drugs.

The reason why they are so well distributed - apart from the fact that they have been used for more than 60 years - is because they have no perceptible odour or taste, they do not produce discoloration, they are pH neutral, they have low toxicity (see below), they have a broad spectrum of anti-microbial activity, they are biodegradable (a forgotten fact) and they are cheap!!!

The total consumption from all sources has been estimated as 76mg/day with 1mg/day from food, 50mg/day from cosmetics and personal care products and 25mg/day from drugs.

Regulation for its use

If there is one thing I have heard a lot through the requests is that a lot of you are worried that the cosmetic industry is self-policing and that there is no true government guidelines or standards.

The truth is that although cosmetics don't have to go through the grueling process of clinical trials like pharmaceutical products have to, there are still strict guidelines as to WHAT is safe and in HOW much quantity it is.

For example in the US, there is such a Code for Federal Regulations, and a Federal Food, Drug (FDA) and Cosmetic (CIR) Committees that regulate all that. In Australia, it's called NICNACS. In Europe, we have  regular Scientific Committees on Consumer products commissioned by the European Commission, etc...

Also, the industry that makes the cosmetics has a strong interest in rigorously testing chemicals before marketing them, just to avoid consumer complaints, lawsuits and product recalls that cost them much more money. In the US, by law, any cosmetic that hasn't been adequately tested must bear the label WARNING: the safety of this product hasn't been determined.

When a new product is being developed, scientists conduct an extensive review of scientific studies and proceed with laboratory tests that haven't been done yet. Their goal is to identify potential hazards, including effects on the reproductive and respiratory systems, effects of the product in the eyes in case of accidental splash, and potential to cause cancer with long-term exposure. They then make a risk assessment which typically includes extra margin of safety to protect against unexpected adverse effects.

Now, although some studies show some toxic effects of certain products on animals, it is important to remember a few points. First, when testing a chemical, it is usually done at a very high concentration that is irrelevant to our actual human consumption ie. they would test 100% pure solution intensively when we are only using a tiny amount of a diluted solution of a few % (thinking about moisturizer for example). Secondly, in all the scientific papers I read, they are testing parabens (but it does apply to other chemicals) through different routes that would not happen in real life ie. most studies use feeding or insertion through the skin with a needle as a method of administration when we are only rubbing it on our skin (except with Lipstick where there is always ingestion no matter how careful you are!!). They are doing so to test the "maximum" toxicity products can have on our body but it's not necessarily what's going happen to us when using creams/shampoos!

Metabolism
Parabens are well absorbed through the skin and although there are differences between the different esters (methyl- ethyl- propyl-, etc...) , none of them accumulate in the body.
Note: In our products, additives such as polysorbate 80, polyethylene glycol or PEG 400 decreases paraben  absorption through the skin while increasing anti-microbial activity.
In fact, in a pharmacological study that used oral administration, there was decreasing amount detectable in the blood as early as 1 to 2 hours after ingestion. After 30 minutes, you could already detect its metabolites (=degradation products) in the urine. Paraben metabolites are p-hydroxybenzoic acid and its glycine-, glucuronic- and  sulfo- conjugates (=salt forms of p-hydroxybenzoic acid).
In an in vitro study, scientists found that liver and kidneys enzymes are extremely powerful at destroying parabens into its metabolites (that eventually end up in our urine as above). Which means that Parabens don't stay as such in our body and are being degraded pretty quickly.
However, and from there arose the big scare, Parabens as themselves - not metabolites - have been detected in human breast tumors, albeit in tiny amount (in nanograms) (Darbre et al., 2004) and those parabens molecules were suggested to originate from cosmetics and in particular deodorant/anti-perspirants (Darbre, 2003 and Darbre, 2008).
This DOESN'T MEAN that parabens presence is the cause of cancer, the author says it herself that more appropriate controls need to be done such as a comparative study between cancer tumors and normal breast tissue (see below for discussion).

Cause for concern? 

• Paraben mimics oestrogen and messes up with our reproductive system and fertility?

In humans, no studies have been conducted on assessing reproductive toxicity of Parabens to fully characterize potential human health hazards.

However, In vitro and In vivo studies (cells in culture and mice/rats, respectively) have shown that Parabens have a very small oestrogen-like activity. They are capable of binding the Oestrogen receptor but to do so they have to be at a concentration 1 000 to 1 000 000 times higher than the Oestrogen itself, and that high concentration is nowhere near the little amount we encounter in our products!!  Methyl-Paraben was the least oestrogenic with Propyl- and Butyl- being the highest oestrogenic. The p-hydroxybenzoic acid, which is the first Paraben metabolite appearing extremely fast after Paraben ingestion, is completely inactive! 

• Paraben causes breast cancer?

Oestrogen is a major factor in the growth and development of the majority of cases of human breast cancer. It has been suggested that the use of Parabens in cosmetics and expecially in deodorants and anti-perspirants might contribute to the high incidence of this type of cancer. Parabens were detected in tissue samples from human breast tumors. Of the parabens, 60% were Methyl-Paraben, others were Ethyl-, Propyl-, Butyl- and isoButyl-. However not only they were found in Tiny amounts (in nanograms) but Methyl-Paraben was shown in previous studies to be the less potent in oestrogenic activity. It has to be noted that in that famous study (Darbre, 2004) that sparked the whole controversy on Parabens, there were no control tissues to demonstrate specificity of association between Parabens and breast cancer, ie. normal healthy tissues could still contain Parabens and be harmless, the presence of Parabens not being the cause of cancer but merely an innocent spectator. To date, no other study has repeated this 2004 study with the appropriate controls. There were however two epidemiological studies (by questioning patients, no lab testing involved) attempting to address the link between breast cancer and deodorant/antiperspirants. One reported no difference of use between cancer patients and non cancer people. The second one reported an earlier onset of the breast cancer with the use of  underarms cosmetics. But again, both studies lacked appropriate controls and certainly lab experiments to attest the presence of Parabens.

• Paraben is generally toxic?

In none of the studies carried out over the course of 60 years, were ever Parabens found to be toxic as regards to the animal weight, behaviour, food consumption, mortality and survival times or organs shape or functionality for any of the Paraben, except for isoButyl-Paraben where body weight was slighly decreased in the group of animals that were fed with the highest dose tested (about 4 to 5 times the usual amount present in cosmetics).

• Paraben is an irritant?

Skin - 100% pure Methyl-Paraben was found to produce mild skin irritation when tested on animal skin, while product containing the usual amount of it (0.2-0.8%) did not produce, or very little, irritation.

Diluted or Undiluted Ethyl-Paraben produced no irritation. Diluted Propyl- and Butyl-Parabens produced inconsistent results varying from none to mild skin irritation.

Eye - None of the Parabens at their diluted concentrations (normally found in products) showed any sign of eye irritation.

Sensitization (=repeated tests to see if reaction develops after additional product applications)- When administered under the skin with a needle, no sensitizing potential was found for either each Parabens, nor for combination of Methyl/Propyl-. In another study, Butyl-Paraben was found to have some sensitizing potential when 6 out of 20 animals developed an allergic reaction.

Case reports in Humans - Several reports of adverse reactions to Parabens and Benzoates in sensitive people have been published. However it has been shown that sensitive people can use Parabens-containing care products on other parts of their body or are not allergic to, for example, Paraben-containing medicines. So for sensitive people, they just need to test what's right for their own skin.

Can we avoid preservatives?
No! In January 2008, in a hospital in Barcelona, there was an outbreak of a deadly bacteria amongst intensive care patients. It turned out that as it was common practice to apply moisturizer after washing intensive care patients, the lotion was at fault. Investigators realised the lotion was "preservative-free".

Alternatives to Paraben
Although all companies seem to agree that there are no preservatives as safe, as colourless, as inert, as stable and as cheap as Parabens, they have had to look at alternatives to satisfy the consumers:
- Lonza company offers the Glydant serie (hydantoin), Glycacil (iodopropynyl butylcarbamate) or mix of those two, as well as Lonzaguard (benzethonium chloride).
- Schulke and Mayr company offers Euxyl PE 9010 (phenoxyethanol and ethylhexylglycerin) and Euxyl K 500 (diazolidinyl urea, sodium benzoate and potassium sorbate mix). Of note, this last name is one of the new organic compounds that are being studied as replacements for Parabens, however, although they are effective against mould and yeast, they show minimal effectiveness against bacteria.
- Most of the companies also offer combination of Parabens with other components:
Schulke and Mayr offers Euxyl K 300 (phenoxyethanol, methyl-, butyl-, ethyl-, propyl-, isobutyl-Parabens).
Clariant company offers Phenonip XB (phenoxyethanol/methyl-, propyl-, ethyl-Parabens).
For a complete list of preservatives and suppliers, visit this article on the Happi website (Household and Personal Products Industry).

Please note that other known preservatives such as quaternium-15, dimethyl-dimethyl (DMDM) hydantoin, imidazolidinyl urea, diazolidinyl urea, sodium hydroxymethylglycinate and 2-bromo-2-nitropropane-1,3-diol are formaldehyde-releasing preservatives (a whole new chapter of whether or not this is safe could be opened)!

Natural alternatives have also been explored but such preservatives tend to lack in robustness needed to adequately control bacteria and fungal growth. Moreover, batch-to-batch consistency (in efficacy, safety and odor) is very difficult to accomplish albeit is essential. Also the fundamental issue to bear in mind is whether or not they are any safer than synthetic technologies. Note: Parabens are actually of Natural origin!
Bio-Botanica supplies 3 patented natural preservatives that are essential oils, some extracts, various glycols and some chemistries that have antimicrobial activity. One of their representative says that "the biggest benefits are their natural names and the comfort level with consumers". However they are not as potent as traditional preservatives and need to be added in higher quantity, becoming major components of a formulation, therefore worries about safety, stability, odour and colour need to be included into the equation!

References

Soni M.G., Carabin I.G. and Burdock G.A., Food and Chemical toxicology (2005) 43:985-1015.
Darbre P.D., J.Appl.Toxicol. (2003) 23(2): 89-95.
Darbre P.D., Aljarrah A., Miller W.R., Coldham N.G., Sauer M.J., Pope G.S., J.Appl. Toxicol. (2004) 24(1): 5-13.
Darbre P.D. Short communication, Breast Cancer research. (2008) Supplements 11/S3/S5.
Scientific Commitee on Consumer Products, European Commission, 28 January 2005.
Health Claims against cosmetics (2005) American Council on Science and Health.
Happi Website
Safecosmetics.org