Wednesday, December 14, 2005

Everyday Patents - Mouthwash

I’ve started looking out for patents on everyday things since I’m thinking a lot about intellectual goods at the moment. It’s easy to imagine that patents should be for big ideas; in fact, they’re usually for very mundane improvements. Since patents leave a bad taste in some people’s mouths, I’ll start with Listerine.

The label on my bottle of CoolMint Listerine discloses two patents: one for the formulation (5,891,422) and one for the design of the bottle (D316,225). I’ll ignore the design patent – who knew that one could patent the shape of a bottle? – since the chemistry is more interesting: the invention is an effective mouthwash formulation that reduces the amount of ethanol, which has to date been a key active ingredient.

Ethanol kills mouth bugs, but the patent application says that “there have been objections to it on heath grounds”. (Since humanity has been getting high on the stuff for millennia via an endless variety of alcoholic beverages, it’s not clear to me what these objections might be – unless The Prohibition Is Back. Perhaps some kids are getting drunk drinking Listerine? Stranger things have happened in the US…) Unfortunately, if you reduce the amount of ethanol, a mouthwash doesn’t work as well. It also doesn’t taste or look as good, because the solubility of other ingredients (like thymol, menthol, and eucalyptol) is reduced

Warner-Lambert’s chemists found that alcohols having 3 to 6 carbon atoms work just as well as ethanol, if not better. (Ethanol has two carbon atoms.) The example given in the patent disclosure is 1-propanol.