The product must be not merely dangerous but unreasonably dangerous. Most products have characteristics that make them dangerous in certain circumstances. As the Restatement commentators note, “Good whiskey is not unreasonably dangerous merely because it will make some people drunk, and is especially dangerous to alcoholics; but bad whiskey, containing a dangerous amount of fuel oil, is unreasonably dangerous.…Good butter is not unreasonably dangerous merely because, if such be the case, it deposits cholesterol in the arteries and leads to heart attacks; but bad butter, contaminated with poisonous fish oil, is unreasonably dangerous.” 1 Under Section 402A, “the article sold must be dangerous to an extent beyond that which would be contemplated by the ordinary consumer who purchases it, with the ordinary knowledge common to the community as to its characteristics. ”
Even high risks of danger are not necessarily unreasonable. Some products are unavoidably unsafe; rabies vaccines, for example, can cause dreadful side effects. But the disease itself, almost always fatal, is worse. A product is unavoidably unsafe when it cannot be made safe for its intended purpose given the present state of human knowledge. Because important benefits may flow from the product’s use, its producer or seller ought not to be held liable for its danger.
However, the failure to warn a potential user of possible hazards can make a product defective under Restatement, Section 402A, whether unreasonably dangerous or even unavoidably unsafe. The dairy farmer need not warn those with common allergies to eggs, because it will be presumed that the person with an allergic reaction to common foodstuffs will be aware of them. But when the product contains an ingredient that could cause toxic effects in a substantial number of people and its danger is not widely known (or if known, is not an ingredient that would commonly be supposed to be in the product), the lack of a warning could make the product unreasonably dangerous within the meaning of Restatement, Section 402A. Many of the suits brought by asbestos workers charged exactly this point; “The utility of an insulation product containing asbestos may outweigh the known or foreseeable risk to the insulation workers and thus justify its marketing. The product could still be unreasonably dangerous, however, if unaccompanied by adequate warnings. An insulation worker, no less than any other product user, has a right to decide whether to expose himself to the risk.” 2 This rule of law came to haunt the Manville Corporation: it was so burdened with lawsuits, brought and likely to be brought for its sale of asbestos—a known carcinogen—that it declared Chapter 11 bankruptcy in 1982 and shucked its liability. 3