Author: Marie Hartley, Staff Writer, 2010.
Iodine is a natural element that is essential for all living organisms. Iodine is a member of a group of non-metal elements called halogens; other halogens include fluorine, chlorine and bromine.
Iodine is used topically, orally and by injection:
Iodine may also be ingested in foods such as seaweed, seafood and iodised salt. Smaller amounts of iodine are found in vegetables and meat.
The term ‘iodine allergy’ is commonly used, but is actually a misnomer. Iodine is a trace element present throughout the body, and is essential for the production of thyroid hormones. It is not possible to have a true allergy to elemental iodine.
These reactions may be classified as immediate and non-immediate:
Newer iodinated contrast media have improved chemical properties and the incidence of these types of reactions is now much lower.
Most of the above reactions to contrast media are not true hypersensitivity reactions (immunoglobulin E antibodies are not involved). The reactions are called idiosyncratic, and unlike true hypersensitivity reactions, previous sensitisation to the agent is not required, nor do these reactions consistently recur in an individual.
|History of a previous reaction to iodinated contrast media||
|History of asthma, food allergy, or allergy to other medications||
|Significant cardiovascular disease or use of beta-blocker medications||
Povidone-iodine is a commonly used antibacterial agent that is a compound of iodine and povidone, along with other additives. Povidone is also used in other products such as foods, medicines (e.g. antihistamines, diuretics and pain-relievers), hair products and toothpastes.
Allergic contact reactions to povidone-iodine preparations are rare, and can be difficult to distinguish from an irritant contact reaction to povidone-iodine. Both reactions can cause redness, induration (firmness) and multiple small blisters.
Patch testing is often used to help diagnose an allergic contact reaction. However, false positive reactions can occur in this instance due to the irritant properties of povidone-iodine under occlusion. When a positive patch test reaction to povidone-iodine does occur, it is important to confirm results with further tests, such as the repeat open application test (ROAT).
See the DermNet NZ bookstore
© 2018 DermNet New Zealand Trust.
DermNet NZ does not provide an online consultation service. If you have any concerns with your skin or its treatment, see a dermatologist for advice.