The case, reported by the “New England Journal of Medicine”, of a young woman aged just 26 who suffered sudden kidney failure after using an apparently harmless hair cream has caused quite a stir. Doctors who treated the patient revealed that she had used a product that contained 10% glyoxylic acid. Pietro Manuel Ferraro, Full Professor of Nephrology at the University of Verona, spoke about the nature of this compound and the possible links with renal failure, clarifying the possible health risks that products based on glyoxylic acid can represent, providing advice to all those who use it.
INSIGHTS
Professor, what is glyoxylic acid?
Glyoxylic acid is a chemical compound that is metabolised by the liver, transformed into another compound called glycine through an enzyme called alanine-glyoxylate aminotransferase or transformed, again at the liver level, into oxalate through another enzyme that It is called lactate dehydrogenase.
Why is it used in some personal care products? In what kind of products can we find it?
Glyoxylic acid is used as a hair straightener as it has the ability to interact with keratin, which is the main component of the hair. It interacts with keratin making the hair smoother. Over time it has replaced formaldehyde for this purpose, which was initially used as a hair straightener, but which was then banned due to its teratogenic and carcinogenic effect, i.e. it increases the possibility of tumor formation.
Glyoxylic acid is mainly found in hair straighteners.
Can it actually pose a health risk?
In fact, over the years, data have been accumulating relating to the potential renal toxicity of glyoxylic acid, with the description of cases of acute renal damage, therefore of a sudden and also important reduction in renal function which has been correlated precisely with the use of hair products. It was believed in early reports that this was due to the presence of glycolic acid, while in reality more recent data points to glyoxylic acid as a potential culprit. The mechanism believed to be at the basis of the potential toxic damage of glyoxylic acid is linked to its metabolism, to its transformation into oxalate in the organism. Oxalate is a molecule that, once formed, must be eliminated almost exclusively through the kidneys. Therefore, in conditions of increased oxalate production, its concentration within the renal tubules can greatly increase. A characteristic of oxalate is precisely that of binding very strongly with calcium, forming calcium oxalate crystals, which on the one hand can directly obstruct the renal tubules, and on the other give rise to an inflammation process which involves ultimately the clinical picture of acute kidney injury. It must be said, however, that, in light of the available data, a certain predisposition to this type of toxic damage is very likely necessary since, for example, in several patients who have had acute kidney damage following the use or exposure to glyoxylic acid , there was already a history of kidney stones, therefore a tendency towards the formation of calcium oxalate crystals or in any case pathologies that lead to immune hyper-reactivity such as psoriasis. Therefore, to date, it is not easy to predict a possible toxic response of the organism to exposure to glyoxylic acid.
Is the possibility of kidney damage (with all the clarifications you have made) linked to the simple use of the product on the skin or is it necessary to ingest it (even small parts, perhaps during washing)?
It is not necessary to ingest it, the hypothesis is that it is absorbed through the skin. In fact, the work published in the NEJM reports the development of renal damage in mice in which the product was applied to the fur/skin.
Do you feel like giving advice to those who use these products?
To date there is no scientific data so robust and solid as to inform a precise recommendation on this point. In some of the cases described, clinical information such as a renal biopsy or crystalluria examination was not available to allow a causal link between exposure to glyoxylic acid and the development of acute kidney injury. Furthermore, as mentioned, it is possible that there are predisposing or precipitating factors, so it is not currently possible to give a recommendation that applies to everyone. Certainly, it is useful to pay attention (after using these products) to the development of signs and symptoms which can also be very non-specific such as nausea, vomiting, general malaise. In these cases, where the picture does not normalize spontaneously, it is advisable to seek medical advice for further investigation.
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