Fatigue Symposium 2025: L'Oreal Bond Building Presentation Announced

The ‘Symposium on the Fatigue Testing of Hair’ will take place on Thursday 15th May.  Today we are pleased to announce that Dr Nawel Baghdadhi (L’Oréal Research and Innovation, Aulnay-sous-Bois, France) will be speaking about From Science to Disruptive Hair Repair Consumer Perceived Innovation Technology. This event, co-organized with Dia-Stron Ltd, will be a hybrid event. A very limited number of places are available to join the symposium live at TRI. There are, of course, unlimited paces on-line, and the event will be streamed live, and on playback as usual.

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Over the past decade, Single Fiber Fatigue Testing has become the hottest new testing technique in the hair care industry. This methodology often yields substantially larger differences between samples, in terms of breakage tendences, than those obtained by traditional tensile testing. It also highlights the sizable contribution of previously unrecognized factors and considerations to the breakage process, which can be used to derive potential new strategies for breakage avoidance. It is already possible to see fatigue data being used in product and ingredient claims communications. In their presentation, the L’Oréal team show how fatigue testing can be incorporated into claims support packages focussed on bond repair claims. Dr Baghdadhi’s abstract reads as follows:

Human hair is a complex organic fiber primarily composed of proteins self-assembled into keratin intermediate filaments, cross-linked by a dense disulfide network. This intricate structure imparts remarkable physical properties, including a diverse range of curl patterns [1]. Regardless of hair type, however, hair is susceptible to damage. In addition to proteins, hair comprises lipids and various minerals derived from both endogenous (internal) and exogenous (external) sources, with calcium being the most abundant.

A variety of factors can compromise hair's structural integrity. Chemical treatments like coloring, perming, and bleaching; physical treatments like heat styling; mechanical stresses from combing and braiding; and environmental factors like UV radiation can all alter the internal and external structure of the hair fiber. Damage leads to the degradation of amino acids and the disruption of the bonds that hold them together, compromising the overall hair architecture. This damage is a significant concern for consumers, motivating the search for effective repair routines.

Repairing active ingredients are specifically designed molecules that target the damaged hair structure. Notably, these actives can eliminate excess exogenous calcium ions and interact strongly with the hair via ionic bonds, thereby rebalancing and strengthening its internal structure.

Using a combination of techniques, including cyclic fatigue testing, differential scanning calorimetry (DSC), and elemental analysis, we identified citric acid as a potent repairing active ingredient in vitro on hair tresses subjected to various forms of damage.

We will present the results of incorporating citric acid into two product ranges: Kérastase Première and Redken Acidic Bonding Curls. In vitro testing using the different techniques demonstrated the repairing efficacy of these routines. Furthermore, consumer testing across diverse hair types confirmed the perceivable benefits of these routines.

This work reveals a synergistic combination of mechanisms contributing to hair repair, including calcium chelation, pH adjustment, and non-covalent bond networking. The inclusion of citric acid, among other active ingredients, in hair care routines can effectively reinforce hair damaged by chemical treatments, and this benefit is readily perceived by consumers with various hair types.

[1] Loussouarn, Geneviève, et al. "Worldwide diversity of hair curliness: a new method of assessment." International journal of dermatology 46 (2007): 2-6.

[2] Chemical and Physical Behavior of Human Hair, C.R. Robbins, Springer, New York (2002)

[3] Duvel, L., Chun, H., Deppa, D., Wertz, P.W. Analysis of hair lipids and tensile properties as a function of distance from scalp. Int. J. Cosmet. Sci.  27, 193–197 (2005) 

[4] Qu, W., Guo, X., Xu, G., Zou, S., Wu, Y., Hu, C., Chang, K., Wang, J. Improving the Mechanical Properties of Damaged Hair Using Low-Molecular Weight Hyaluronate, Molecules. 27 (22), 7701 (2022)

[5] Zhang, D. Baghdadli, N., Greaves, A. Reinforcing chemically treated human hair with citric acid. Int. J. Cosmetic. Sci.  00, 1-13 (2025)

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