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When people say they are allergic to iodine they may be saying so for a lot of reasons. One of the most common of these is that people are allergic to shellfish, which, in the past, has been used synonymously to describe iodine allergy. There is a possibility that a shellfish and iodine allergy may occur in the same person, but the two are typically unrelated, with shellfish allergy being a response to proteins in the fish. What this tends to mean is that unless a reaction has occurred specifically to iodine, most people can’t tell they’re allergic by inferring a connection between iodine and shellfish.
The matter of being allergic to iodine is rather confusing and, at times, deeply important from a medical standpoint. Iodine is used on the skin during many first aid procedures and prior to many surgeries, and a sudden skin reaction could be very serious. Iodized contrast media may also be injected into the body during different types of scans that could include contrast echocardiograms or contrast computed tomography (CT) scans, and such injections might result in a systemic reaction that could include anaphylactic shock. Yet not all people who react to injections also react to exterior contact with iodine from topical medicines.
It would be greatly useful if people who were about to undergo testing with radio contrast media could simply have a trial run or skin scratch test to determine if they were allergic to iodine. These tests do not exist, however, making it challenging to determine in advance who might have a reaction. Generally, if people have had a reaction in the past, other contrast media substances might be used instead, and if a person cites shellfish allergy, this could be a reason for wariness. Alternately, if patients get sick eating foods that do contain iodine, like iodized salt, greater watchfulness is needed during contrast tests, and sometimes additional medicine is used to stave off a potential reaction.
To this end, some responsibility is on the patient. Other allergies, allergy to shellfish or previous reaction to contrast media need to be brought to the attention of medical providers. Citing that a person is allergic to iodine is not enough, since this doesn’t give health professionals the information they need. Moreover, stating an allergy to iodine is a little inaccurate because people don’t have a histamine reaction to iodine. Instead there is release of histamines due to the elements in contrast dye; it’s a fine distinction, but an important one.
A preponderance of evidence that a person might be “allergic to iodine,” may be managed in several ways. There are other contrast media types like non-ionic forms that could be used instead, lowering reaction incidence in sensitive people. Another way to address this situation is to simply keep watch during administration and be prepared to counter a serious reaction if it occurs. Again, patients must participate too, by citing and explaining any allergies and by making certain doctors know if a contrast media reaction, particularly a severe one, occurred before.
Among its medical applications, iodine has historically been used as a disinfectant. Did it become less popular as such because it worked as an irritant, making way for other antiseptics such as hydrogen peroxide and witch hazel astringent?