The first use of a stent was in the coronary artery in 1986. Since that time, stenting has become commonplace for a variety of medical conditions. All stents used in arteries or veins have some component of nickel in them. As stenting has increased worldwide, many patients and physicians have questioned the safety of stents in those with nickel allergies. By “allergy” I mean someone who gets an itchy red rash if an object with nickel, such as costume jewelry comes into contact with the skin.
All stents used in arteries or veins have some component of nickel in them.
Nickel is one of the most common causes of allergic contact dermatitis — a skin rash or irritation caused by touching a particular substance. It is estimated that nearly 18% of people in North America are allergic to nickel, including 11 million children in the U.S.! Nickel comprises 20% of the earth’s core and is extremely common in our environment. It is not the mere presence of nickel that causes an allergy; rather it is the ability of a metal to release nickel on to the skin that causes an allergy. For example, a poorly constructed low quality metal belt buckle may easily release nickel on the skin and cause a rash in a nickel allergic patient. On the other hand, high grade stainless steel would not release enough nickel to cause a rash because the nickel is so tightly bound within the steel.
It is not the mere presence of nickel that causes an allergy; rather it is the ability of a metal to release nickel on to the skin that causes an allergy.
When most people think of allergic contact dermatitis, poison ivy/oak/sumac often comes to mind. This is known as rhus dermatitis and is easily recognizable by most licensed physicians. For this reason, testing is not needed to prove the diagnosis. However, there are thousands of other less common substances in our environment that have the potential to cause allergic contact rashes in certain individuals. The gold standard to diagnose allergic contact dermatitis is through a painless and noninvasive office test known as epicutaneous patch testing which is performed on the skin by dermatologists and some allergists.
The most common allergen (a substance that causes an allergic reaction) found on patch testing in the United States is nickel. Evidence shows that many people first become allergic to nickel from body piercing. There is a direct correlation in the US between the number of body piercings a person has and the rate of allergy to nickel. There are strict bans in Europe on the use of nickel on objects that touch or pierce the skin and hence there is a much lower prevalence of nickel allergy in Europe.
There is a direct correlation in the US between the number of body piercings a person has and the rate of allergy to nickel.
Now that you have some background on nickel allergy and patch testing, let’s explore the answer to two questions that are likely on your mind…
First, will a substance that causes an allergic reaction on the skin, also cause a problem when implanted inside of an artery or vein? Second, what type of adverse reaction could occur if someone was allergic to the metal in the stent?
Medical stents are mostly made of metal and are commonly used to maintain blood flow to the legs, heart, brain, and other organs. A variety of metals are used including stainless steel which often contains nickel, chrome, cobalt and other metals. Some stents are made of nitinol which is a mixture of titanium and nickel.
The two main concerns are that if a person is allergic to the metal it may lead to inflammation in the blood vessel or a rash all over the skin. Inflammation can lead to narrowing (stenosis) or clotting (thrombosis) of the stent which in turn would reduce needed blood flow. A rash all over the skin and rarely other symptoms such as fever and shortness of breath could also develop
The good news is that adverse reactions involving allergy to metal in stents seems to be very rare. Unfortunately, there are no large studies to prove this. There are individual cases of patients allergic to nickel that developed body rashes or stenosis of the stent. There are also a few slightly large retrospective studies showing a higher rate of nickel allergy in patients with stent stenosis. However, retrospective studies are limited because they look back in time at patients as opposed to prospective studies which look ahead and try to predict what will happen. Unfortunately, large prospective studies do not exist.
Patch testing of patients for allergy to nickel and other metals is not routinely recommended prior to placing a stent because the positive predictive value – the probability that a patient with a positive patch test truly has a nickel allergy — is not very high. In the rare case when a patient self-reports a history of nickel allergy, pre-stent patch testing should be considered but is not mandatory. It is reasonable in certain instances to perform patch testing if a patient strongly desires to know if he or she has metal allergy. There are medico-legal ramifications as well.
To add to the complexity of stents and nickel allergy is the indication for the stent. When someone suffers from a heart attack and needs life-saving treatment, whether or not the patient has a nickel allergy is often not discussed. One would assume that most people would proceed with getting a stent, even if there was a known nickel allergy. On the other hand, chronic deep vein thrombosis (DVT), May Thurner syndrome, Nutcracker syndrome, and pelvic venous insufficiency are complex venous conditions that affect quality of life but are not life threatening conditions and therefore do not warrant placement of an emergent stent.
So what does a patient do? The answer unfortunately is not a clear one. Weighing the benefits and risks of stent placement must be discussed with your physician. One thing that is clear is that the patch testing for nickel allergy prior to stent placement is fraught with dilemmas and that no perfect solution currently exists. The competing desires to minimize societal cost of testing everyone, reduce liability exposure when patients and physicians have concerns, and promote evidence-based medicine have created a difficult puzzle for us to navigate and more studies are needed.
Honari G Ellis S, Sood A. Cutaneous metal sensitivity as a potential risk factor for intra-coronary stent restenosis. Dermatitis. 19(6):352-353, Nov/Dec2008.
Thyssen JP, Engkilde K, MennéT, Johansen JD, Hansen PR. No association between metal allergy and cardiac in-stent restenosis in patients with dermatitis-results from a linkage study. Contact Dermatitis. 2011 Mar;64(3):138-41.
Schalock PC, Crawford G, Brod B, et al. Patch testing for evaluation of hypersensitivity to implanted metal devices. Dermatitis 2016 Sep/Oct;27(5):241-7
Markel K, Brod B, Jacob SE. Letter to the editor: Metal hypersensitivity reactions in the context of Essure ™. Case Rep Womens Health 2018 Oct; 20: e00087
Romero-Brufau S, Best PJM, Holmes DR, et al. Outcomes after coronary stent implantation in patients with metal allergy. Circulation: Cardiovascular Interventions 2012; 5: 200-226
Bruce A. Brod, MD, MHCI, FAAD is the Director of Occupational & Contact Dermatitis and a Clinical Professor of Dermatology at the University of Pennsylvania Perelman School of Medicine. He is the past president of the American Contact Dermatitis Society. He graduated from the University of Pennsylvania Perelman School of Medicine and completed his residency at the University of Pittsburgh in 1991.
Dr Brod has been recognized for his work in political advocacy. He had a lead role in helping the legislature in his state enact indoor tanning laws. He has also taken a lead role in establishing safeguards in teledermatology, access to sunscreen for children, and access to medications through his work with the state medical society. For over a decade, he has been consistently recognized as one of the leading dermatologists in regionally and nationally.