If a product liability action is instituted by an allergic user of a product on the grounds of negligence, the manufacturer or supplier of a product that is harmless to most normal persons will have no liability to the unusually susceptible plaintiff, unless he had reason to know or actual knowledge that some persons are sensitive to the product or to one of its ingredients.  A “plaintiff’s unusual or rare idiosyncratic sensitivity does not provide a basis for recovery under any theory of product liability.”[1]

            To illustrate this, in a suit to recover damages for eye and throat irritation and the collapse of the airway in the plaintiff’s throat, allegedly caused by allergic reaction to materials used in the construction of a motor home, the court held that liability may be found when the plaintiff is a member of an identifiable and significant class of consumer, composed of the innocently allergic.  Liability would be denied, however, if the plaintiff was shown to be unique in susceptibility to the content of the product involved.[2] 

            The same principles controlled a case where the plaintiff had an allergic reaction to an ingredient in a cosmetic that she had applied to her face.  The court held that since it was abundantly clear that the defendant manufacturer had not possessed actual knowledge of the harm the product might cause to some people, and the state of the art at the time of purchase was not sufficient to make it reasonable to charge the defendant with such knowledge, the plaintiff could not premise liability on the ground of negligent failure to warn.[3]

            Implicit in the cases described above and in other decisions is the theory that if the manufacturer has actual knowledge or reason to know that its product contains an ingredient to which some people are allergic, it must give a warning of the danger.[4]  There are some contrasting decisions, however, holding that a manufacturer or supplier may be under no duty even if it knows of the danger, in instances of unusual allergic susceptibility of the plaintiff.[5]

            This latter line of pro-defendant authority was “readily distinguished” in Sterling Drug, Inc. v. Cornish,[6] a case where the plaintiff suffered irreversible impairment of vision as a result of taking Aralen, a drug prescribed in the treatment of arthritis.  The trial court in Cornish instructed the jury that if the manufacturer had known or should have known that a group of people would suffer rare side effects, the defendant had a duty to warn the medical profession of the susceptibility of such a hypersensitive or idiosyncratic group.  On appeal, the defendant contended that this was error, but the appellate court rejected that position.  It stated that:

Under the facts of this case, we believe the better view is that appellant did have a duty to warn.  The instant case is readily distinguishable from those cases denying relief to hypersensitive or idiosyncratic plaintiffs.  Those cases cited by appellant deal with over the counter retail products.  The denial of relief seems to be based on the unforeseeability of the injury and the futility of a warning even if given.  It is said to be unreasonable to expect a manufacturer to foresee that some few persons among its many customers will suffer a rare allergic reaction to some ingredient in the product.[7]

            The court also noted that with prescription drugs, if a doctor is properly warned of possible side effects to some patients and of symptoms that normally accompany those side effects, there is an excellent chance that injury can be avoided.

            An important factor in some of the decisions denying the duty to warn is the number of users who suffer an allergic reaction to the product.[8]  A complaint was dismissed in a case against Procter & Gamble that involved an allergic reaction to a product of which, at the time of the complaint, the company had sold some 225 million units.  The product, a dandruff shampoo, led to reports to the company of approximately 600 adverse reactions, of which three were the kind suffered by the plaintiff in the instant case.  The court held that under these circumstances, there would be no duty to warn users of that particular risk.  The court made the argument that requirements of warnings for cases such as this one would lead to an overabundance of warnings on products and the consequential devaluing of the effectiveness of individual warnings.  It stated that, on the facts of the case before it, the vast majority of even normally allergic individuals would run a statistically insignificant chance of a reaction; rare individuals like the plaintiff, who are potentially allergic to almost everything, might be well advised to test almost all products before making intimate bodily use of them.[9]  A further factor in the court’s decision was that the particular allergic reaction involved in the case was unpredictable, so that a warning would not have been useful even to the tiny minority of users who were potentially at risk.