When products are labeled natural, the court challenges begin, raising questions about whether labeling is really misleading or simply fodder for a lawsuit.

In recent years, one bright spot in an otherwise lackluster market for packaged foods, beverages and consumer products has been merchandise promoted as “natural.”

Consumers, increasingly wary of products that are overly processed or full of manufactured chemicals, are paying premium prices for natural goods, from fruit juices and cereals to shampoos and baby wipes.

But as a spate of lawsuits and consumer advocacy efforts show, one person’s “natural” is another person’s methylisothiazolinone.

The problem, consumer groups and even some manufacturers say, is that there is no legal or regulatory definition of what “natural” is.

The debate in many ways echoes the tussling in the 1990s over the word “organic,” when foodmakers played fast and loose with the term and frustrated consumers tried to make sense of it all.

The United States Department of Agriculture, tasked with creating an “organic” program, was pestered by consumers, farmers, manufacturers and states as it developed a definition, guidelines and a certification process.

Today, while regulators are weighing whether to define the term “natural,” the lack of clarity for over the past decade has resulted in a freewheeling, and litigious, environment.