Methylchlorisothiazolinone and methylisothiazolinone are two ingredients that are used in skin care and cosmetic formulations to preserve products against the growth of bacteria, yeasts and fungi. They are generally used in water-based formulations rather than oil-based or wax-based products.
Methylchlorisothiazolinone and methylisothiazolinone have a slightly bad reputation in the beauty industry for being a standardized chemical allergen. This means that they have been linked to allergic reactions.
Methylchlorisothiazolinone and methylisothiazolinone
The good: Methylchlorisothiazolinone and methylisothiazolinone help ensure product safety by preventing the growth of bacteria, yeast and mold.
Not so good: Methylchlorisothiazolinone and methylisothiazolinone are known allergens, and although their use is limited to low concentrations, they can be irritating to some skin types.
For whom is that? All skin types except those identified as having an allergy.
Synergetic ingredients: Works well with most ingredients
Keep an eye on: Many blogs and articles list these two ingredients as “toxic” ingredients. That is actually not entirely true. The toxicity depends on the concentration. Anything can be toxic in the right concentration. The main problem with methylchloroisothiazolinone and methylisothiazolinone is the increased risk of irritation and allergies.
Why are methylchlorisothiazolinone and methylisothiazolinone used?
Methylisothiazolinon and methylchlorisothiazolinon are preservatives. Preservatives are one of the most important parts of the formulation process. Preservatives can be either natural or synthetic in nature and are designed to prevent the growth of bacteria, yeast, and mold.
Preservatives are important in any formulation as they ensure the safety and quality of the product. However, they are especially important for water-based formulations. This is because water-based formulations are more prone to spoilage and microbial growth, as water is important to the growth of many microbes. Contamination of your product can occur through use, e.g. B. when you scoop out the product with your hands or when you leave the lid off the product for a certain period of time.
If a product is spoiled by microbial growth, it can lead to discoloration, unpleasant smells or a disruption of the texture and consistency. Outside of the sensory aspects of the product, however, spoilage can also increase the risk of infection or irritate the skin.
While methylisothiazolinone is occasionally used alone in formulations, it is usually combined with methylchlorisothiazolinone. In the past, methylisothiazolinone and methylchloroisothiazolinone have been used in both dishwashing and dishwashing products. Dishwashing products are products such as detergents, soaps, shampoos, etc. that should be rinsed off the skin after a short time. Leave-on products are products such as moisturizers, lotions, make-up, etc. that are intended to be left on the skin. As you can imagine, they have different levels of interaction with the skin because of the different amounts of time they spend. This difference can determine security and sensitivity.
More recently, some manufacturers have removed these ingredients from their leave-on products due to concerns about increased skin sensitivity to methylisothiazolinone in leave-on formulations.
Are Methylchlorisothiazolinone and Methylisothiazolinone Safe?
According to the US Food and Drug Administration, Methylisothiazolinon and methylchlorisothiazolinon are considered allergens. In high concentrations, outside the range of skin care regimens, methylchloroisothiazolinone can cause burns and skin irritation. Most of the reported reactions to methylchloroisothiazolinone in the 1980s and 1990s were seen in products left alone at a higher concentration than currently used.
Because of these problems with allergic reactions, methylchloroisothiazolinone has largely been removed from leftover products and is only used in low concentrations in flushable products.
According to the US Food and Drug Administration (FDA), methylchloroisothiazolinone is a standardized chemical allergen. The current rate of contact allergies or the likelihood of an allergic reaction is around 8 percent.
The concentrations at which methylisothiazolinone and methylchlorisothiazolinone are currently used are up to 15 ppm or ppm in dishwashing products and 8 ppm in cosmetics. The Panel of Experts for the Review of Cosmetic Ingredients, an independent group responsible for evaluating the safety and effectiveness of skin care and cosmetic ingredients, reviewed the available data Methylisothiazolinone and methylchloroisothiazolinone. The panel of experts found the two ingredients to be safe for use in current concentrations and specified applications. The data suggest that methylisothiazolinone is safe up to 100 ppm when used alone.
In 2013, the panel of experts re-evaluated new data on these two ingredients. These new data suggest that methylisothiazolinone is more allergic to left-on products than previously thought. In response to this finding, the panel of experts concluded that methylisothiazolinone and methylchloroisothiazolinone are safe in their current uses and concentrations. However, the panel of experts advocated lowering the concentration of methylisothiazolinone in products left in place in order to reduce allergic reactions.
The panel of experts also warned people who know they are allergic to methylisothiazolinone to avoid personal care products that contain methylisothiazolinone.
CIR, 1992. “Final Report on the Safety Assessment of Methylchlorisothiazolinone and Methylisothiazolinone,” Journal of American College of Toxicology, vol. 11, no.1.
Pónyai G, Németh I, Temesvári E. Sensitivity to Methylchlorisothiazolinon / Methylisothiazolinon and Methylisothiazolinon in Hungary. Dermacol Res Pract. 2016; 2016: 4579071.