Whether you had a case depends on whether there was something defective about the product: that is, whether it was designed or manufactured improperly (e.g. it was contaminated during manufactur) or had inadquate instructions or safety warnings. Inadquate warnings, in this case, means judged by a standard of "reasonableness"--the warnings don't need to warn against every possible harm, only those that are reasonably foreseeable. For example, say that you had a very rare allergic reaction to a properly formulated, properly manufactued producut. In that case, it is likely that the manufacturer is NOT liable, since they do not have  to guard against every possible ill or harm, and if your reaction is sufficiently rare, it would not be reasonable require them to put a warning on the box, jar, etc. On the other hand, if your reaction is moderately common one, they might have had to warn against it, the way food manufacturers often warn against peanut allergies. Or if the problem was too high a concentration of a certain ingredient was used--a dangerously high concentration--that could give rise to liability. So the manufactur must have basically done something wrong in developing, manufacturing, and/or labeling/instructing about the product to be liable; if it was instead that you had horribly bad luck in having a violent reaction to a product that 99.9% of people can use safely, they might not be responsible.The best way to proceed is to discuss the matter with experienced product liability counsel, who can evaluate the situation and advise as to whether you may have a case and what it might be worth.