In medicine, well intended advice often proves wrong. Sometimes, such recommendations are repeated for years until we lose sight of the where/how the ideas originated. It then takes well documented research to retract the outdated ideas—even then correction is often resisted. An example is the frequently repeated advice that women allergic to seafood should not undergo a hysterosalpingogram (HSG). This rationalization is due to the fear that the iodine-containing contrast that is used to perform the test may provoke a reaction in sensitized patients[r1] .
Food allergies occur in about 4% of the population[r2] . Seafood is among the most common of the foods that people are allergic to. Shellfish and seaweed are the most common foods that contain high levels of iodine. That fact aside, it is difficult to establish how the concern between seafood allergy and iodine first originated. True allergies result when your immune cells react to a protein—not a mineral like iodine—by producing antibodies. These antibodies can then create a reaction upon repeat exposures to the allergen (protein that the person is allergic to). A true seafood allergy is typically a response to a protein called tropomyosin. There is no tropomyosin in the HSG contrast. Therefore, a classical allergic effect isn’t possible.
A recent review [r3] of the medical literature confirmed that the actual risk of a reaction to the contrast is rare. In fact, the odds of a severe reaction were far less than 1% (0.02-0.5%). So given the importance of the information obtained by performing an HSG, most patients benefit from this part of the infertility evaluation.