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When her first son was diagnosed with type 1 diabetes (T1D), small town Missouri mom Kayla Mattingly was understandably upset. But life with T1D soon developed into a “new normal,” and that helped her believe she was prepared for anything when her second young son was also diagnosed. Unfortunately, the family encountered a new nightmare: This boy developed a rare insulin allergy that makes it painful for him to take the insulin he needs to survive.

D-Mom Mattingly recalls how both of her young sons were diagnosed just after their first birthdays. But it was only her second son Thatcher, now 6 years old, who developed this rare and dangerous allergic reaction to his insulin.

And it’s not just one type of insulin, but all of them. His symptoms were red, hot, irritated skin with hard knots at the insulin injection sites or where a pump infusion set is located, and those fill up with pus and are painful.

“It’s a vicious cycle, and we can’t pinpoint it or why it’s happening. But some days are worse than others,” Mattingly told DiabetesMine.

Little Thatcher is one of only a handful of people worldwide known to have developed this type of severe insulin allergy, a subset of a more generalized insulin allergy that is estimated to impact about 2 to 3 percent of people treated with insulin.

“He’s been dealing with this since he was 2, and it’s definitely traumatic for him,” the D-Mom said, a slight tremble rising in her voice over the phone. “Our big worry is that as they get older and hit puberty, things will get a lot worse.”

Kayla Mattingly and her boys with T1D, Baker and Thatcher

The Mattingly family has four boys, currently ranging in ages from 10 to 1 years old.

Their first son Baker, now 10, was diagnosed with T1D just after his first birthday. Their second son, Sadler, was 5 months old at the time of Baker’s diagnosis. Life went on and they “got into the groove” of life with T1D. And then they had their third son, Thatcher. He began presenting T1D symptoms right after his first birthday in 2016.

Initially, both boys were on a basal-bolus MDI (multiple daily injection) regimen, and everything seemed fine.

But then both boys began insulin pumping in late 2018, and just a few months later, the family first noticed that Thatcher — then about 2 years old — was developing problems at his insulin infusion sites within 24 hours of putting them into his skin.

At the spot where the insulin went into his body, he’d develop hard knots that began turning red and leaking puss. It wasn’t every pump site at first, so Mattingly thought maybe it was a site infection — especially since her older son Baker was not having those same issues despite using the same Tandem t:slim X2 pump.

Mattingly talked with her son’s diabetes care team about the notion that she possibly carried MRSA (Methicillin-resistant Staphylococcus aureus) and passed that along to her son, leading to skin infections due to bacteria. They used alcohol swabs at every site and bathed him in Hibiclens pre-surgical skin cleanser to try and ease the skin reactions. Mattingly even wore gloves and a face mask while caring for her son, trying to limit any possible exposure to irritants. But nothing worked.

“You’re really going through a checklist with all of this, wracking your brain,” the mom told DiabetesMine. “We’re all thinking, and even our endo team is thinking, ‘Surely it can’t be the insulin!’ We were trying everything.”

The Mattinglys tried many different ways to navigate around the problems Thatcher experienced, before eventually finding their way to an insulin allergy diagnosis.

  • They tried switching from Humalog to Novolog insulin, in hopes he had a small aversion to preservatives or ingredients in one insulin versus another. It didn’t make a difference after about 4 months of switching between those insulin brands.
  • They tested different insulin pump infusion sets with metal cannulas and different adhesives, too. One option was the Medtronic i-Port, which allows you to take an injection without puncturing the skin with an infusion set. That didn’t work, either.
  • They stopped insulin pumping in mid-2019, after Thatcher had a severe seizure. They tried longer syringes and different types of needles for his insulin injections. Mattingly recalls seeing welts on the back of his legs and arms where he was getting those injections, and at the time, thinking they were mosquito bites since it was summertime.

“I wasn’t looking for it with the injections, and it truly was oblivious,” she said, pointing out that the realization came during a family trip to Chicago, when she watched a skin reaction materialize just following an injection. They switched back to Novolog and later Apidra insulin, but the allergic reactions continued.

Finally, they were directed to have Thatcher undergo skin patch testing, where doctors draw a grid of squares on your skin to test reactions to particular allergens and ingredients. They put all the different types of insulins on Thatcher’s skin, to see what would happen. They also tested saline, often used as a proxy in insulin pumps, but Thatcher had no sensitivity to that.

They also picked his forearms and did deeper injections of .001 units of insulin, as well as other preservatives contained in each particular insulin. Sure enough, Thatcher tested positive for all types of insulin, including the old-school Humulin insulin first available in the mid-1980s.

Beyond all the skin reactions, Thatcher was also just not processing insulin correctly.

“Some days you could dose and dose and it was like water. His sugars would be over 300 mg/dL. But then all of a sudden, he’d crash,” his mom said. “He’d go from needing 4 to 5 units of Lantus a day to nothing, or a half-unit max for 2 weeks. It’s a vicious cycle, I told the doctor, and Thatcher was miserable.”

During this whole time, Mattingly says her endocrinologist helped navigate the costs of all the insulins and diabetes supplies, with industry reps donating to the family and their insurance covering most of the costs so they weren’t hammered with sky-high medical bills.

They received a formal insulin allergy diagnosis in late 2019.

Research points to three main types of “hypersensitivity reactions” to insulin that exist:

Type I reactions, the most common, are due to insulin preservatives that include zinc, protamine, and meta-cresol. These are topical reactions that happen in the immediate aftermath of an insulin injection.

There is also a Type II hypersensitivity, but that’s not associated specifically with insulin in most of the published research.

Type III reactions, also referred to as serum-sickness reactions, are delayed Arthus reactions characterized by localized subcutaneous nodules that appear 4 to 6 hours after an insulin injection. These are extremely rare.

Type IV reactions are T-cell mediated reactions that are the most delayed and the most rare. They tend to occur within 8 to 12 hours of insulin use, peak at 24 hours, and last anywhere from 4 to 7 days.

A 2011 clinical study notes that approximately 2 percent of individuals on insulin experience some kind of aversion to insulin, but less than one-third of these events are considered a direct reaction to the insulin itself, as most are caused by the preservatives.

The most severe and most rare, Type IV, is the kind Thatcher was diagnosed with, meaning he has a specific T-cell response to all types of insulin. It’s another autoimmune reaction in his body, just like T1D itself, and his parents fear that he may not grow out of this allergy as he gets older.

“You can’t just turn that off, so it’s forever,” Mattingly explained.

Mattingly says the big insulin manufactures — Eli Lilly, Novo Nordisk and Sanofi — weren’t particularly helpful in offering ways to address this, other than providing information about ingredients and preservatives in their insulins and documenting the adverse effects.

Per a 2017 clinical study analysis that reviewed nearly three decades of research going back to before insulin analogues were first introduced in the late 1990s, there is no established course of treatment for dealing with insulin allergies.

“Based on the available literature… it is clear that hypersensitivity reactions occur, but it is difficult to determine the ideal treatment approach,” that clinical study review states.

Experts are still experimenting with treatments, such as this 2019 study that showed some alleviation of allergic reactions using a mixture of biphasic insulin aspart 30 and dexamethasone.

Dr. Kyle McNerney, the Mattinglys’ physician at St Louis Children’s Hospital, says, “Insulin allergy is a very rare condition that can be extremely challenging to treat. Insulin allergy can interfere with how patients take care of their diabetes and is potentially life threatening. Patients can have reactions ranging from subtle skin changes to severe, life threatening anaphylaxis.”

McNerney says it takes time to test the specific reactions patients are having, and he often recommends consulting an allergist. While they can sometimes pinpoint a particular insulin product or delivery method that’s to blame, or even treat with medication, it’s not always a clear-cut process.

Currently, Thatcher is taking Methotrexate to help suppress the reactions, but the Mattinglys are searching for more solutions as the medication is only a “Band-Aid” to an ongoing, underlying problem; the Methotrexate doesn’t fully suppress his reactions and they’re worried what will happen as the boy’s insulin needs increase as he gets older.

His insulin pump sites only last for a day usually, so they need to switch them out much more frequently than the typical 2 or 3 days that infusion sets are labeled to be worn on the body.

There are other options that the family has yet to explore to help offset Thatcher’s allergy:

Diluting insulin. This can often be looked at as a potential help, but because Thatcher is so young, the family hasn’t yet tried different combinations of diluting insulin mixtures to see what may be less irritating to the skin.

Intravenous (IV). They also haven’t gone this route, but are keeping it in mind with their diabetes care team. This would require hooking up an IV every time Thatcher needed insulin.

Desensitizing. Clinical research studies (here and here) show that “desensitizing” the body to insulin can be effective for certain insulin allergies. This is done by giving the patient antihistamines and corticosteroids (even Benadryl) before administering small amounts subcutaneously or by IV. Mattingly says her family’s medical care team has informed her that this option doesn’t work with her son’s more severe Type IV hypersensitivity because his reactions are so delayed.

Afrezza inhaled insulin. This has also come up, but the family has been hesitant to try it since this white powdered form of insulin is not yet approved by the Food and Drug Administration for use in children, and there are concerns about what impact his allergies could have if triggered in his lung tissue.

Pork and beef insulin. The animal versions of insulin used before the first synthetic human insulin was OK’d in the 1980s are not widely available anymore. Mattingly says she wouldn’t want to try something that they wouldn’t be able to get their hands on regularly.

“Patients living with an insulin allergy have to be creative and adaptable to try and find a solution that keeps their insulin allergy under control so they are able to receive insulin necessary to survive and thrive with diabetes,” McNerney said.

While insulin allergy is rare, Thatcher is certainly not alone.

Another D-mom who’s dealt with this is Jaclyn Smith in North Carolina, whose 13-year-old son Jack has lived with T1D and an insulin allergy since he was 2.

“For some crazy reason that nobody can explain, Jack’s reactions wax and wane,” she told DiabetesMine, noting that he’s currently doing OK with Novolog delivered through an Omnipod patch pump. “We change sites more frequently, but pumping is his best option because reactions are horrific to every long-acting insulin on the market.”

Mattingly wants to help connect these parents for moral support, and to lobby the medical and research community to start paying more attention to this topic.

In mid-2021, Mattingly and a group of eight other impacted D-Moms teamed up to create a new advocacy group called Insulin Allergy and Hypersensitivity Awareness (IAHA). They are seeking nonprofit status as they work to bring more light to this little-discussed issue.

Their logo is an antelope named Patchy, after those red and pink splotches that appear on the skin (and fur) due to insulin allergy.

The group of D-Moms had been talking for many years online, but it took a near-death experience in 2020 for Mattingly to turn this idea into reality.

After a high-risk pregnancy in the first year of the COVID-19 pandemic, the Mattinglys welcomed their fourth child — another boy, of course — into the world. Collier was born in August 2020, and Mattingly says she almost didn’t survive his premature birth.

Following that experience, Mattingly says she felt called to do something about the insulin allergy issue. She believes that mission is why she survived.

With IAHA, they’re hoping to connect dots among doctors, researchers and other healthcare experts active in this area, who hone in on identifying the causes and what can be done to better address it.

“Insulin has been the answer for 100 years, but now it’s not the answer for us,” she said. “We know there’s a need and it’s not being addressed. Eight may not seem like a lot, but one is too many when they can’t rely on what they need to survive.”

Mattingly added sadly about her son,” He’s been through a lot and is very brave, but he looks at me and says, ‘Mom, I don’t know why my body doesn’t like my insulin.’ It’s heartbreaking.”

To learn more, visit the #HopeForThatcher campaign that aims to raise awareness about insulin allergy and the new IAHA organization.