The EU cosmetic regulations make clear that mouthwashes are one of the categories of cosmetic product. They are explicitly listed as an example, and obviously fit the definition. Elsewhere in the regulations, there is a distinction made between products that are left on, and those that are rinsed off. This is important because it affects the way that allergens need to be listed – there is a lower cut off value for allergens to be listed on leave on products.
This is presumably to allow for the fact that leave on products have a greater potential for the allergens to penetrate the skin in the event of a product that is left in contact with it. But whatever the reasoning, it means that when you create a cosmetic product you need to assign it to one category or the other. They didn’t create a gurgle for a while then spit it out category.
Often this distinction is clear. Shampoos for instance are pretty unambiguously rinse off products, while moisturising creams are definitely left on. But there are a few grey areas – would a clay masque which is left on until it is dry count as a leave on because it is left on for some time, or does the removal of the clay after use make it a rinse off? And how about mouthwashes? These on the face of it are pretty much in the rinse off camp. After all, the contact time is short and the product is rapidly sent down the drain.
But when I consider the intention of the regulations, I am inclined to assign them to the leave on category. Although the contact time is indeed short, it is to a part of the body which has a very good blood supply and where penetration into the body is quite easy. I feel that if I was allergic to something I’d rather take a chance applying it to my skin than putting it in my mouth. You also need to consider the odd individual who doesn’t get the whole mouthwash concept and simply drinks it. So although a mouth wash is a rinse off product by any consideration of the meaning of the english language, I would label it as if it were a leave on one.
You are entitled to disagree. The EU cosmetic regulations throw up these kinds of issues all the time. It is the big problem with any kind of legislation – every rule is drawn up with a particular set of circumstances in mind and often makes sense in typical cases. But there are always fuzzy edges.