When Morgan McElroy suddenly stopped being able to smell and taste earlier this month, she wasn’t all that surprised. Her mother, whom she lives with in Dayton, Ohio, had recently started showing symptoms of covid-19, the disease caused by the novel coronavirus, and McElroy, 20, figured that she had also been infected.

What McElroy didn’t expect, though, was to find herself in the emergency room a day later — swollen and covered in a red, itchy, hivelike rash that was spreading all over her body.

“I’m allergic to covid,” McElroy said in a TikTok video documenting her dramatic experience that has been viewed more than 4.6 million times.

But while her symptoms looked like an allergic reaction, experts say it is “highly unlikely” that McElroy developed an actual allergy to the novel coronavirus.

“She’s not allergic to covid,” said Purvi Parikh, an allergist and immunologist with the Allergy and Asthma Network, who has seen several covid patients reporting similar reactions. Rashes are “frequently known consequences of viruses and usually benign,” Parikh added. “Actual allergies can be life threatening. . . . It would be misleading to suggest you could be allergic to a virus.”

Instead, the symptoms McElroy developed are more likely a byproduct of her immune system fighting the coronavirus, said David Stukus, a member of the covid-19 response task force for the American Academy of Allergy, Asthma and Immunology.

“We know that covid really can be a systematic disease for a lot of people” he said. “When it comes to covid-19, anything and everything is in play.”

Viruses and other infections are common triggers for seemingly random episodes of hives and swelling, Stukus said, adding, “It can be very dramatic, especially when somebody’s face swells; nobody wants to see that. It can be very debilitating because it can be severely itchy, but it’s very different than an allergic reaction and anaphylaxis.”

McElroy told The Washington Post she started to get the sense that something wasn’t right when she woke up Dec. 3 with an unusual itching sensation inside her mouth. She took Benadryl and lay down for a nap. But when McElroy got up a couple of hours later, what she saw in her bathroom mirror sent her running to get her mother.

“My face was absolutely swollen to the max,” McElroy said. “I immediately went in panic mode.” She noted that it also felt like her throat was swelling, which prompted her mother to call 911.

By the time the ambulance arrived, McElroy said, her symptoms had worsened. “It was getting pretty gross, and my lips were just absolutely humongous. Everything was just massive.”

At the hospital, McElroy said, she was given two steroids through an IV and liquid Benadryl. In addition to the swelling, much of her body was covered in itchy red splotches.

“They asked me the questions like, ‘Are you using new laundry detergent? Did you eat anything new?’ ” McElroy recalled. “And I was like, ‘Guys, I’ve been in quarantine for over a week. I haven’t done anything new.’ So I was like, ‘I promise you, it’s nothing that I did. It just popped up out of nowhere.’ ”

After about two hours at the hospital, McElroy was sent home with a prescription for Prednisone, which has anti-inflammatory effects, and an explanation for what happened that left her with more questions than answers.

“What my doctor said in there was, ‘I think it’s covid-related,’ ” she said. “But that’s all the explanation that they had.”

To call McElroy’s reaction an allergy oversimplifies the immune system’s complex responses, said Panagis Galiatsatos, an assistant professor of medicine at Johns Hopkins.

“It just means her immune system doesn’t like covid, no different than every other human being’s immune system,” said Galiatsatos, a pulmonary and critical care doctor who works with covid patients.

Rashes and swelling triggered by infections are most commonly seen in young children, Parikh said, which may be why “it freaks adults out a little bit more” when it happens to them. Still, Parikh emphasized that there is usually no need to panic.

The allergy-like symptoms are probably the result of a person’s immune system becoming “a little too overactive in its task to clear the infection,” she said.

This reaction, Parikh noted, is not believed to be connected to the other types of rashes caused by the coronavirus, including the unusual frostbite-like patches that have been observed on people’s toes and sometimes fingers. What McElroy described on TikTok “is more similar to what we see with viruses in general,” Parikh said.

One theory is that an overactive immune system can cause the release of histamine, similar to what happens when the body encounters an allergen. “The virus kind of mimicked an allergy,” Parikh said.

McElroy, whose symptoms have mostly cleared up, posted a second video on TikTok noting that she knows she isn’t actually allergic to covid and that histamine release triggered by the infection was a more probable cause of her symptoms.

It’s possible in cases of covid-related reactions, Stukus said, that the virus is “unmasking somebody who is predisposed to have hives and swelling.” For instance, many people with allergies — environmental, food or otherwise — have allergy cells that are “really good at releasing this histamine chemical.”

“When they get sick with an infection and their immune system goes into overdrive to fight that off, they can just activate those cells as a byproduct,” he said.

Aside from viruses alone triggering the symptoms, other potential causes may be linked to factors like drinking alcohol and vigorous exercising, which can increase blood flow and temporary inflammation in the body, Parikh said. Taking common medicines such as Advil and Motrin could also cause rashes and swelling, especially when combined with a virus, she said.

If people are worried about how the coronavirus may affect them, Stukus recommended that they “take a deep breath and use trusted resources.”

“We have a lot to learn in regards to all the nuances involved with this infection, and if you have any concerns about your personal health, always call your doctor first,” he said.