The Cosmetic Ingredient Review Expert Panel (CIR) has reached a final conclusion on the use of methylene glycol in nail hardeners and hair/keratin smoothing products. Also considered was the maximum allowable limit of formaldehyde, which is normally found in trace amounts when methylene glycol is used as a cosmetic ingredient. Additionally, the CIR reviewed the erroneous and often conflicting information related to the chemistry of methylene glycol and formaldehyde. Although the CIR did a very good job addressing much of the misinformation surrounding this issue, in the process they also created additional confusion.

Right from the start of this review process (Nov, 2010), the CIR deserves tremendous credit for correcting some very long standing chemical misinformation by stating, “The apparent good solubility of formaldehyde in water is actually the good solubility of methylene glycol in water and the capacity of the solution to accommodate small polymethylene glycols (i.e. two to ten methylene glycol units long).  Formaldehyde itself is only sparingly soluble in water. The rate of the hydration reaction is relatively fast (i.e. the half-life of formaldehyde in water is 70 ms) and the equilibrium between methylene glycol and formaldehyde strongly favors methylene glycol, at room temperature.” 1  This reflects the scientific reality that 37% formalin is actually not 37% formaldehyde, but instead 59% methylene glycol in equilibrium with 0.05% formaldehyde and 10-15% methanol, as a stabilizer to prevent polymerization.

The next question addressed was to determine if using 37% formalin in natural nail hardeners was a safe cosmetic application.  After reviewing the information presented by the Nail Manufacturers Council (NMC) of the Professional Beauty Association,  the CIR determined, “given the rapid reaction on the nail surface and the use of nail hardeners at room temperature, the expert panel did not consider that formaldehyde/methylene glycol at 1-2% in nail hardeners would pose a risk of sensory irritation to the eyes and nose or throat of users.” Therefore nail hardeners continue to be considered “safe as used” by the CIR Expert Panel.

The CIR also addressed use of methylene glycol in hair smoothing products.  Independent research studies presented by the Professional Keratin Smoothing Council (PKSC) demonstrated that typical salon exposures to formaldehyde gas are well below OSHA safety guidelines, however the expert panel was divided over whether or not these products could be used safely.  After hours of heated debate, it was agreed that exposures under some conditions of use were sufficient to cause sensory irritation and this raised concerns that proper ventilation and safety procedures were not uniformly followed nor have adequate steps been taken by manufacturers to ensure that these products are safe for use in hair salons.  The panel placed the burden on manufacturers to show how sensory irritation could be eliminated and until such a time, the CIR concluded that hair smoothing products containing formaldehyde/methylene glycol are unsafe. The CIR suggested reducing the formaldehyde/methylene glycol concentration in hair smoothing products, controlling the amount of product applied, reduction of temperatures used during treatments, and the use of adequate ventilation should be considered by manufacturers to address the reports of adverse reactions related to sensory irritation.

The CIR adopted a suggestion to include limits for formalin concentration, rather than formaldehyde or methylene glycol since formulators actually use 37% formalin in cosmetic products. They concluded that, other than nail hardeners, cosmetics should not contain more than 0.2% (w/w) of 37% formalin. Unfortunately, they erred in their calculations claiming that this amount of formalin contains 0.118% methylene glycol and 0.74% formaldehyde.  When properly calculated, the actual amount of formaldehyde is 0.000093% or 0.93 ppm.2  The NMC is submitting a request to the CIR to correct this error.

The question of the formaldehyde releasing preservatives (actually methylene glycol) was not addressed in this safety assessment. Even so, the CIR stated, “the formaldehyde releasers may continue to be safely used in cosmetics at levels established in their individual CIR safety assessments.”

The hair smoothing issue was hotly debated amongst the CIR panel and it’s likely that further discussions are needed to address several outstanding issues.  As more is being learned about the chemistry, this will surely influence future discussions.  For example, the PKSC presented some extraordinarily interesting data from an independent research laboratory, based on earlier work by Utterback, et. al. 3, which demonstrates that methylene glycol exists in air and can be isolated separately from formaldehyde gas.  This research also demonstrated that when formalin is vaporized on a 450oF flat iron, the predominant species in air is methylene glycol and not formaldehyde gas, as believed.  This is likely due to the equilibrium chemistry of formaldehyde and methylene glycol which greatly favors the latter in the presence of water vapor. This new information is likely to be of interest to researchers and regulators around the world and the debates are likely to continue.

1. CIR Expert Panel Meeting, Buff Book 1, Formaldehyde, Dec. 13-14, 2010

2. Winkelman, J.G.M., Voorwinde, O.K, et. al.,  Kinetics and Chemical Equilibrium of the Hydration of Formaldehyde, Chemical Engineering Science, 57, pg. 4067-76, 2002.

3. Utterback, D.F., Gold A., Millington, D.S., Quantitative Analysis of Formaldehyde Condensates in the Vapor StateFormaldehyde: Analytical Chemistry and Toxicology, Advances in Chemistry, Vol. 210, pg 57-65, 1985


Doug Schoon is an internationally-recognized scientist, author and educator with over 30 years experience in the cosmetic, beauty and personal care industry. He is a leading industry authority, known for his technical and regulatory work that has helped shape the beauty industry. He is Co-Chair of the Nail Manufacturers Council (NMC), and as Creative Nail Design’s (CND) Chief Scientist, was head of the R&D laboratory, QA, and Field Testing/Evaluation departments for almost 20 years. Schoon has authored several books, video and audio training programs, as well as dozens of magazine articles about salon products, safety, and best practices for salon professionals. Schoon is well known for his captivating presentation style and his unique ability to make complex concepts easy to understand. In 1986, Schoon founded Chemical Awareness Training Service (CATS) – the beauty industry’s first safety training company. This was followed by his book, Nail Structure & Product Chemistry, 1st and 2nd Edition, which has become essential reading for nail salon pros. Schoon is a chief contributor to Milady’s Standard Nail Technology and Standard Cosmetology, as well as several medical reference books such as Baran and Maibach’s Textbook of Cosmetic Dermatology and Cosmetic Dermatology: A Comprehensive Medical and Surgical Text. Schoon serves as an expert witness in legal cases, and doctors, dermatologists and podiatrists often consult Schoon when writing articles, books or scientific papers. He has worked as a scientific researcher, author and lecturer for almost 35 years and holds a Masters Degree in Chemistry from UC-Irvine. He currently resides in Dana Point, CA. Overview Industry Experience President, Schoon Scientific + Regulatory Consulting, LLC (2007- present) Co-Chair, Nail Manufacturer’s Council (NMC) (2003-present) V.P., Science & Technology – CND (Creative Nail Design, Inc.(1987-2007) Executive Director/Founder of Chemical Awareness Training Service (1986-89) World renowned expert; considered a leading scientist in the field Works with state, federal and international regulators to develop beauty industry related standards and regulations. Experienced working with EU and Japanese cosmetic regulatory agencies and many domestic and international trade associations Experienced working with activist groups to address industry issues Over thirty years experience as a researcher, lecturer, author and educator Regularly writes articles and makes contributions to several domestic and international beauty trade magazines Author of science and safety books for beauty professionals, including the industry standard, “Nail Structure & Product Chemistry“, Second Edition, 2005 Contributing author to many educational books used in beauty schools Contributing author to several medical texts used by dermatologists and doctors Bachelors Degree Chemistry, Cal State University- Long Beach, CA (1982) Masters of Science Degree in Chemistry, University of California-Irvine (1984)

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