Gluten intolerance: Is there a risk with cosmetics containing it?

Whether by choice or due to intolerance, an increasing number of people are adopting a gluten-free diet. According to a survey conducted in 2019, around 8% of the French population do not consume products containing gluten. Gluten intolerances can be divided into three categories: coeliac disease, a genetic autoimmune disease characterised by an inappropriate immune response to gluten, non-coeliac gluten sensitivity, causing abdominal pain and difficulties in digesting gluten, and wheat allergy, resulting in classic allergic reactions mediated by Immunoglobulin E.

According to European regulations, a food product labelled as "gluten-free" must contain less than 20 ppm of gluten.

In this context, it is understandable for individuals suffering from any of these conditions to question the potential risks posed by cosmetics containing gluten. Indeed, although cosmetics are not intended to be ingested, it is possible to consume a small amount, whether it be from eating a midday sandwich with residual cosmetic traces on one's fingers or from applying lip balm or lipstick. However, even if these products do indeed contain gluten, it is unlikely that a significant amount would be ingested during normal use. In fact, if a 4g lipstick contains less than 20 ppm of gluten, it contains less than 0.002% of gluten. This means that if the entire tube of lipstick was consumed, less than 0.08 mg of gluten would be ingested.

To ensure this, a study conducted in 2018 sought to determine whether it was common for cosmetics that could potentially be ingested during their use to contain gluten. This protein was measured in 66 products intended to come into contact with the mouth, including 37 toothpastes and 10 lip balms. The study's findings showed that 94% of them could be considered "gluten-free" according to the definition provided by European regulations, as they contained less than 20 ppm of gluten. The highest concentration of gluten analysed was 35 ppm. The authors concluded that the risk associated with gluten in cosmetics was very low. However, although it is low, this risk is not non-existent, which does not completely reassure those who are intolerant to gluten.

Furthermore, another question arises: are individuals intolerant to gluten likely to develop a contact allergy to gluten after applying a cosmetic containing this protein? According to the expert group from the Cosmetic Ingredient Review (CIR), the use of hydrolysed wheat proteins and hydrolysed wheat gluten does not cause skin hypersensitivity reactions in sensitive individuals and does not induce sensitisation when the average molecular weight of the peptides is around 3,500 Da. These conclusions were drawn after studying the various data from available clinical studies. However, it is suspected that the smaller molecules of hydrolysed gluten are capable of crossing the skin barrier and triggering allergic reactions.

Furthermore, the issue of an increased dietary sensitivity to gluten following the application of cosmetics containing it is not so straightforward. Although the scientific literature has not yet addressed this issue in people intolerant to gluten, evidence suggests that the use of cosmetics containing gluten can trigger a dietary sensitivity in people who previously tolerated this protein. Notably, there is the case of a hospital in Japan which, over the course of two years, received 18 patients who suffered from urticaria or anaphylaxis after consuming foods containing wheat. These individuals had not previously shown any allergy to gluten but had recently started using a wheat-based soap and indeed tested positive for the protein present in the soap. After ceasing to use the cosmetic, only one person stopped showing a sensitivity to gluten.

In the absence of irrefutable data on the safety of gluten in cosmetics, it is recommended for those with intolerance to exercise caution when choosing their skincare products.