“The thing about drug allergies is that it’s not always what you initially think,” is the philosophy that guides Paul Bigliardi, MD, a University of Minnesota Physicians dermatologist and allergologist. 

A significant piece of Dr. Bigliardi’s work involves solving mysteries related to allergic reactions patients may have when they undergo treatment for a certain condition, like patients who need an organ transplant or those in the aging population who often take different medicines.

“Patients who receive an organ transplant, for example, may need 10 to 20 different medicines like antibiotics or antirejection drugs,” Dr. Bigliardi says.

He adds, “If they have an allergic reaction to one of them, it can be dangerous, which makes it important for a doctor to evaluate the potential allergies to help keep patients safe.”

This process includes finding out if the patient is really allergic to a drug or class of drugs and, if they are allergic, identifying safe alternatives.

Unpacking the mysteries of these allergic reactions can be difficult, though. There are no reliable blood tests available, only skin tests or exposure to the suspected drug, which doctors only use if it is necessary for the patient’s condition or if the allergy is unlikely. That’s the moment where Dr. Bigliardi’s unique training and background come in.

Trained in Switzerland

Dr. Bigliardi attended medical school in Switzerland, where all allergists have basic training in dermatology. This inspired him to complete two full residencies in dermatology and allergy/clinical immunology, which means he is in a unique position to evaluate various allergic reactions using skin tests for those that involve the skin and mucous membranes. 

These kinds of allergic reactions come in two types: 

  • Immediate type reactions, which occur within minutes or hours after a patient ingests a drug
  • Delayed type reactions, which manifest hours or days after exposure to the drug and can complicate the identification of the source

More complicating factors

Another piece that makes identifying allergies difficult is that, according to Dr. Bigliardi, one third of patients have an allergy reported in their health record, but studies have shown that only about 10% of reported drug allergies are real or correctly reported.

“Imagine being unable to give the most effective drug for a condition or disease, either because there is a real, or worse, a falsely reported allergy,” he says. “In this case, an alternative might have to be chosen with more side effects, is less effective and often more expensive.”

Since there are no reliable blood tests for drug allergies, doctors need to rely on a patient’s history, reactions in skin tests or even re-exposure to the drug in a safe environment to correctly diagnose them.

Getting down to the solution

Dr. Bigliardi’s philosophy is that getting to the bottom of a potential drug reaction is paramount. Often, it may not even be a drug that leads to a reaction since many skin conditions or diseases can mimic one. 

In a case he solved in close collaboration with an anesthesiology team, Dr. Bigliardi remembers  a patient in need of a kidney transplant. “The vital operation had to be postponed twice, because the patient developed an allergic shock during the early phase of anesthesia,” he recalls. 

“And the problem was that nobody knew the cause for these reactions, and it had to be known before operating again.”

All the skin tests for anesthetics and antibiotics used during the early phase of anesthesia turned out to be negative, “However, the anesthesiologist told me that they used a catheter and the tip was treated with a specific antiseptic to reduce infections,” he says. 

“When we tested for this commonly used disinfectant, the skin tests showed a strong reaction after 15 minutes,” he explains, “Which was an indication that the patient was highly allergic to it.”

In the next operation, the team used a catheter without that kind of disinfectant, and it went off without a hitch. “This also shows that solving the drug allergy mystery is a highly multidisciplinary task,” he adds. 

For patients who need an organ transplant, instances like these inspired Dr. Bigliardi and his colleagues across specialties to develop guidelines and questions to ask before their operations. Prior to each surgery, the patient’s medical team fully examines potential allergies, using skin tests to help confirm a reported allergy to a medicine they could use.

And about those elusive blood tests for evaluating drug allergies– Dr. Bigliardi and his team are working on developing one. “If we can create one that’s reliable and effective, that will be a breakthrough to effectively help so many patients,” he says. 

As a professor at the University of Minnesota Medical School, Dr. Bigliardi shares these insights with his students and other healthcare providers to pass the torch to future generations.

That’s where research, clinical care and education come together– where academic medicine lights the way.