The size of the market for drugs to treat allergies has fallen during the first decade of the 2000s. The likely reason for this decline in the value of sales is not a decline in the number of people suffering from allergies, rather it has to do with the fact that generic drugs have come onto the scene to compete with the leading name brand drugs. This was possible because the patents on several of those name brand drugs expired in the middle of the decade.

Geographic reference: United States
Year: 2003 and 2007
Market size: $7.5 billion and $5.1 billion respectively
Source: Medical Marketing & Media, May 2008, page 64.
Original source: IMS Health