Among the brands that have faced legal challenges are several that have long promoted their use of natural ingredients: Tom’s of Maine antiperspirants and toothpastes, the Honest Company’s laundry detergent and dish soap, Annie’s Homegrown salad dressings, Breyers and Ben & Jerry’s ice cream, Aveeno face moisturizers and Seventh Generation dish soap.

“The lawsuits you see are only a fraction of the claims that are made,” said David T. Biderman, a partner at Perkins Coie who defends food companies in class-action lawsuits. Behind the scenes, Mr. Biderman said, plaintiffs’ lawyers are sending letters to companies and threatening to file lawsuits over labels they argue are misleading or violate consumer protection laws. Those letters, Mr. Biderman said, are often rejected, go away or are resolved with a small payment.

Whether the lawsuits are necessary, or a nuisance, depends on whom you ask.

Proponents say that in lieu of clear regulation, consumers have been protected by these lawsuits, pointing to a number of cases in which manufacturers have altered their labels. General Mills, which faced at least two federal lawsuits claiming that its Nature Valley granola bars contained artificial ingredients, replaced labels that once read “100% Natural” to say they are “Made With 100% Natural Whole Grain Oats.”

Corporations, lawyers say, have been reluctant to allow a case to go to trial and risk having a legal definition of “natural” emerge — which might set standards companies would have to meet. As a result, the bulk of the lawsuits filed over the past decade have been settled, dismissed or, more recently, stayed by judges who hope regulators will step in with a definition.

Kim Richman, a plaintiffs’ lawyer, said his clients, including consumers and nonprofit groups, “engage in socially conscious litigation to level the playing field against corporate America as government oversight increasingly falls short.”