Iodine is not usually considered to be an allergen, but some people are hypersensitive to it, and they may be considered to have an iodine allergy.
Iodine is a common element found in the human body. Reactions to iodine are extremely rare, but can be fatal when they do happen. Medical uses of iodine are on the rise, especially in radiocontrast agents used to improve X-rays. Reactions have been more common in recent years. Iodine has even been responsible for deaths in a number of cases.
Exposure to iodine may cause some of the following in hypersensitive people:
- rash (contact dermatitis)
- hives (when ingested)
- anaphylaxis, or a severe life-threatening allergic reaction (very rarely)
Anaphylaxis is a life-threatening condition that requires emergency medical attention.
Symptoms of anaphylaxis include:
- abdominal pain
- difficulty breathing
- heart palpitations
- hives (along with other symptoms)
- nausea or vomiting
- altered level of consciousness
- rapid pulse
Certain solutions and foods can cause an allergic reaction in people who are sensitive to iodine:
- Tincture of iodine, also known as weak iodine solution, is commonly used as a disinfectant in medical settings. It may cause rashes in hypersensitive people.
- Iodine contrast can also cause an allergic reaction. It’s an X-ray radiocontrast agent used for intravenous injections. Contrast dyes containing iodine have been responsible for severe allergy reactions (including deaths) in a limited number of hypersensitive people. If an individual is known to have iodine allergy — he or she must NOT be given iodine contrast.
- Foods that contain iodine can also cause an allergic reaction. Fish, dairy, and soy are sources of iodine.
There are some myths about what actually causes an iodine allergy reaction. Many people believe that you’ll be at risk for having an adverse reaction to iodine if you have a shellfish allergy. This is largely a misconception. Research in the Journal of Emergency Medicine has shown that shellfish allergies are not linked to iodine allergy. The research also shows that having a shellfish allergy doesn’t increase the likelihood that you’ll have a reaction to iodine. Instead, proteins such as parvalbumins in fish and tropomyosins in shellfish are responsible for seafood allergies.
Some topical antiseptics contain povidone-iodine. This is a solution of polyvinylpyrrolidone (PVP) and iodine. Povidone-iodine can cause a serious rash that is similar to a chemical burn in a few rare cases. In patch tests, however, allergic reactions were not caused by the iodine. Instead, they were caused by non-iodinated copolymers in povidone. Povidone alone has resulted in anaphylactic shock in very rare cases.
Diagnosis and Treatment
Your doctor will probably have you do a patch test if she thinks you’re allergic to iodine. During a patch test, the doctor will apply a small amount of iodine to a patch. It’s then placed on your skin. Your doctor will check to see if you had a reaction after a few days.
Once you’ve been diagnosed with an iodine allergy, your doctor may prescribe a corticosteroid cream or oral corticosteroid such as prednisone. These can help relieve symptoms of an iodine hypersensitivity, such as a rash. They’ll also direct you to stay away from foods that contain iodine as well as contrast dyes so you can avoid future reactions.
Anaphylactic shock from an iodine allergy is an emergency situation. It may require immediate medical treatment in the form of a shot of epinephrine (adrenaline).
Amiodarone is a medication that’s used to manage atrial fibrillation in cardiac patients. As of today, experts know of only one case of cross-reactivity between amiodarone and iodine. Doctors should use caution when prescribing amiodarone for such people. However, the risk of an allergic reaction is very low.
While iodine sensitivity and related allergic reactions are uncommon, talk to your doctor about getting tested if you suspect you have an allergy or suffer from some of the symptoms. If you are diagnosed with an iodine allergy, work with your doctor on a diet that will help you to avoid reactions.