Federal agency officials say the manufacturer of the EpiPen failed to investigate claims its product didn’t work properly in some instances.

You might not blame allergy sufferers if they are a bit nervous these days.

“To learn that [the EpiPen] probably wasn’t going to save my child’s life in an emergency was alarming and infuriating,” Lindsay Stril, a Washington state mother of a 7-year-old girl with severe nut allergies, told Healthline.

Stril was carrying around a recalled EpiPen for nearly a year, which she never had to use in an emergency.

“Drug makers of rescue medicines need to have stricter quality control and testing so no lives are ever lost due to a defective EpiPen,” said Stril. “Reports of defective pens should be their No. 1 priority. I think they let us down.”

Stril’s anger surfaced after an announcement earlier this month by the U.S. Food and Drug Administration (FDA).

In a Sept. 5 letter, FDA officials said the maker of EpiPen epinephrine injectors didn’t properly investigate manufacturing problems that caused the devices to fail to work properly.

FDA officials said the failures potentially threatened the lives of people who experience severe allergic reactions.

In its warning letter to Meridian Medical Technologies, a division of Pfizer, officials said the agency had “received hundreds of complaints that your EpiPen products failed to operate during life-threatening emergencies, including some situations in which patients subsequently died.”

“You [Meridian] did not thoroughly investigate these complaints,” according to the FDA letter. “Moreover, we note that your follow up did not include removing potentially defective products from the marketplace, even though you had identified a defect in one of the critical components used to manufacture these products, and even though you ultimately confirmed the same or similar component defect as the root cause for multiple complaints.”

The FDA ordered Meridian to address the issues raised in the warning letter promptly or face possible legal action, up to seizure of the company’s products and injunctions against their sale.

In some cases, FDA officials said EpiPen and EpiPen Jr products (the latter designed for children) didn’t deliver epinephrine to patients undergoing anaphylaxis when the proper activation sequence was performed.

In other instances, the devices erroneously delivered the drug when not activated, leaving injectors empty when needed.

The FDA said in its letter to Meridian, “You failed to thoroughly investigate multiple serious component and product failures for your EpiPen products, including failures associated with patient deaths and severe illness. You also failed to expand the scope of your investigations into these serious and life-threatening failures or take appropriate corrective actions, until FDA’s inspection.”

Meridian announced a voluntary recall of 13 batches of potentially defective EpiPen products on March 31, 2017, following an FDA investigation.

Meridian manufactures EpiPens at a factory in Brentwood, Missouri, for medical-device distributor Mylan Specialty.

In a Sept. 8 press statement, Myland officials said the company “is confident in the safety and efficacy of the EpiPen products being produced at the site.”

“For technology that has been around for decades, I’m frustrated that we as a community even have to question the safety of our medication,” Allie Bahn, who blogs as Miss Allergic Reactor about lifestyle and travel for people with food allergies, told Healthline.

“EpiPens are my safety net. If a mistake happens, I rely on them to save my life. Is that still true? I hope so, but I don’t have that same confidence that I once did. Unreliable medication is not something any of us should have to consider.”

The EpiPen recall was the second time in two years that manufacturers had to pull faulty epinephrine injectors from pharmacy shelves.

In October 2015, Sanofi US voluntarily recalled all Auvi-Q epinephrine injectors from the market due to their potential for inaccurate dosage delivery, including “failure to deliver drug.”

The Auvi-Q recall was based on 26 customer complaints, compared to the hundreds received by Meridian about EpiPen.

Auvi-Q was reintroduced to the market in October 2016 after being reacquired from Sanofi by its inventors via the privately held pharmaceutical firm kaléo Pharma.

The company “conducted a thorough manufacturing assessment and invested in new technology and quality systems to ensure accurate, reliable and consistent delivery from the product,” according to a press statement.

Bahn, a lifelong user of EpiPens, got a prescription to Auvi-Q when it was initially released because as a runner she appreciated its compact design.

“When Auvi-Q went off the market, I felt fortunate that I still carried EpiPens. Now, I’m not sure what to think,” she said. “When Auvi-Q returned, I was tempted to get a prescription but in the back of my mind, I still felt uneasy about relying on it, given its past. Since the news with EpiPen, I called my allergist to request a prescription for Auvi-Q.”

“Right now,” she added, “I don’t have great confidence in either one, and feel frustrated that those are the only options.”