The parabens are an effective class of preservative. A natural product can be assumed to have a certain efficacy when it has a similar efficacy in the environment where it was discovered. According to the Merck Index, methylparaben was identified in the very biological environment where an inhibitor of the growth of microorganisms is most wanted: the vaginal secretion of female dogs in estrus. To escape premature expiration, skin care products need ingredients able to somehow hinder the growth of adventitiously borne, contaminating microorganisms. These products are called preservatives, they need to be efficacious and, most importantly, they must be safe.

The safety of a natural product is assessed either by appropriate laboratory experiments, or by ethno-botanical and historical epidemiological observations showing that a certain product has been used by a certain population for a relevant time duration without adverse effects. For instance, when administered at the usual doses, tea and coffee infusions can be claimed to be safe. It is in fact to be kept in mind that, as pointed out by Paracelsus: “All things are poison, and nothing is without poison; the dosage alone makes it so a thing is not a poison.”


Parabens

Propylparaben was synthetized first in 1887. It has served as template for chemical modifications to generate several derivatives globally called “parabens” that have been used as preservative in foods, beverages and cosmetics for many years (perhaps since 1920).

For some reason possibly associated with the zeitgeist of the end of the Millennium, preservatives were met with dislike from a public that insisted on natural ingredients (whatever it means) and abhorred synthetic ingredients (whatever it means). Parabens were the first target of this cultural movement. They were subjected to further experimentations aimed at assessing or refuting their alleged toxic behavior.

The jury is still out, as they say, but most judges did not wait for the jury to reach its decision. Today, five different parabens have been completely banned in the EU (isopropylparaben, isobutylparaben, phenylparaben, benzylparaben and pentylparaben), while others are strictly regulated because they are believed to be endocrine disruptors. An endocrine disruptor is an exogenous substance or mixture that alters some of the functions of the endocrine system and, consequently, causes adverse health effects in an intact organism or its progeny. The endocrine system is the set of glands and organs that produce hormones that control many important functions in the body, including the so-called sexual hormones.

Some scientists argue that conclusions about parabens being endocrine disruptors come from experimentations on animals that followed different administration routes and used concentrations that don’t represent the use of parabens in skin care products that are applied topically in small quantities. Let’s take an example to compare laboratory results with everyday life.

Butylparaben, believed to be the most “toxic” of all the parabens, is toxic to zebra-fish embryos at a concentration of 10 micromolar¹, that is about 2mg per liter in the fluid that is used in laboratory experiments to permanently surround the embryos in the fertilized egg.

When a consumer applies on her face one gram of skin care product that contains 0.5% butylparaben, she is applying 5mg of paraben that, upon a hypothetical total penetration and dilution in the body, and assuming no cleaning up or elimination, would result in about 0.1 mg per liter if her body mass is 50 kg (~110 pounds). That concentration would be even smaller when the body mass of the consumer is larger than 110 pounds.

This concentration of 0.1 mg/liter is an acute dose (i.e. present only transiently) that is 20 times smaller than the chronic dose (i.e., present permanently) used in the zebra-fish experiment!


Regulatory Guidelines?

The US Food and Drug Administration (FDA) doesn’t have special rules that apply to preservatives in cosmetics. Under the Federal Food, Drug, and Cosmetic Act (FD&C Act), cosmetic products and ingredients, other than color additives, do not need FDA approval before they go on the market. The law treats preservatives in cosmetics the same as other cosmetic ingredients. The FDA does not believe that parabens present a danger to our health when used in cosmetics. Parabens are found in lotion, foundation and plenty of other beauty products. FDA scientists continue to review published studies on the safety of parabens. At this time, there is no information showing that parabens as they are used in cosmetics have an effect on human health.

A 2019 paper states that “Based on currently available scientific information, claims that parabens are involved in the genesis or propagation of these controversial and important health problems are premature. Haste to remove parabens from consumer products could result in their substitution with alternative, less proven, and potentially unsafe alternatives, especially given the compelling data supporting the lack of significant dermal toxicity of this important group of preservatives.”²

To adhere to the feeling of the consumers and in spite of an initial resistance against removing parabens, the vast majority of the new skin care products coming to the market are paraben-free so that the consumer has the choice between paraben-free and paraben-containing skin care products. It is worth noting that the resistance to removing parabens from skin care products was not due to the difficulty in finding alternatives. It was indeed due to the fact that parabens provided lotions and emulsions with particular esthetic properties that are difficult to reproduce when they were removed. 

References

1. Jiefeng Liang et al Assessment of Thyroid Endocrine Disruption Effects of Parabens Using in Vivo, In Vitro and In Silico approaches. Environ Sci Technol 2021 Dec 20. doi: 10.1021/acs.est.1c06562. Epub ahead of print. PMID: 34930008.
2. Anthony F Fransway, Paulina J Fransway , Donald V Belsito, James A Yiannias Paraben Toxicology. Dermatitis. (2019) 30 : 32-45. doi: 10.1097/DER.0000000000000428.

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Paolo Giacomoni, PhD
Insight Analysis Consulting
[email protected]
516-769-6904
 
Paolo Giacomoni acts as an independent consultant to the skin care industry. He served as executive director of research at Estée Lauder and was head of the department of biology with L’Oréal. He has built a record of achievements through research on DNA damage and metabolic impairment induced by UV radiation as well as on the positive effects of vitamins and antioxidants. He has authored more than 100 peer-reviewed publications and has more than 20 patents.