Is It Possible To Have an Allergic Reaction to COVID-19?

It's not uncommon for COVID-19 to cause issues such as a loss of taste and smell, dizziness, or fatigue in the initial stages of the illness. However, one woman went viral on TikTok after saying she had an allergic reaction to the virus in 2020.

Although it is no longer available on the platform, the TikTok video uploaded by user Morgan (@moeemoneeyy) detailed how she contracted the virus from her mom, who tested positive for COVID-19. She added that she and her siblings assumed they would contract COVID-19 too as soon as their mom was diagnosed because they were all in the same household.

"Well, I didn't know that I 'officially' had it until I woke up to my face being swollen like a…balloon," she said. Her mother called 911, and she was taken to the hospital. "I had to ride in the ambulance by myself. My face was having an allergic reaction to COVID. I'm allergic to COVID."

Morgan shared more information in a later TikTok: "Essentially when you have a foreign substance in your body, aka COVID, your body produces histamines to fight off the infection," she said. "Well, when my body came into contact with COVID, it produced histamines. Unfortunately, my body produced way too many histamines to fight off COVID. And overproducing histamines causes swelling to the throat, face, eyes, lips—you name it, I had it—like an allergic reaction."

It certainly seems like another awful consequence of COVID-19, but is an allergic reaction to the virus a legitimate concern? Here's what you need to know, according to allergists and infectious disease doctors.

Generally Speaking, What Happens When You Have an Allergic Reaction?

When it comes to your immune system, its primary purpose is to prevent or limit infection, according to the National Institute of Allergy and Infectious Diseases (NIAID). When it's working properly, your immune system has the ability to distinguish between normal, healthy cells and unhealthy cells.

Additionally, your immune system is made to recognize invaders (i.e., unhealthy cells), including viruses and bacteria, and begin an immune response to try to rid them. The actual process is complex, but it includes your innate immunity, which is your body's initial response to an invader, and your adaptive immunity, where your body sends more specialized immune cells to target a particular pathogen.

However, sometimes the body can overreact to a harmless substance (think: allergens like pollen, latex, mold, dust mites, insect stings, or certain foods), per the American Academy of Allergy, Asthma & Immunology (AAAAI), and cause a release of chemicals called histamines, which can trigger inflammation. In that situation, the release of histamines can cause tearing of the eyes, congestion in the nose, swelling, difficulty breathing, and even vomiting and diarrhea, if there is a food trigger.

So, Can You Have an Allergic Reaction to a Virus Like COVID-19?

No, you can't—but it is possible to experience symptoms similar to an allergic reaction.

"You cannot become allergic to a virus, but many viruses commonly cause allergy-type symptoms because they can irritate the immune system in a way that mimics allergic reactions," Purvi Parikh, MD, an allergist with Allergy & Asthma Network, told Health. Dr. Parikh mentioned that it's possible to have hives, itchy rashes, and swelling with every virus—including COVID-19. "This is actually very common in children and one of the most common causes of hives in children," said Dr. Parikh.

The exact reason for this is unclear, but Dr. Parikh said that it's thought that "over-stimulation of the immune system can cause immune complexes that trigger histamine release."

Prathit Kulkarni, MD, assistant professor of medicine in infectious diseases at Baylor College of Medicine, told Health that the histamine release is "not exactly an allergy to the virus directly, but an infection can 'wake up' an allergic response in the body in general." And though this hasn't been widely reported with COVID-19, "it might theoretically be possible," said Dr. Kulkarni.

When histamine works as part of the immune system to fight bacteria, viruses, or other pathogens, it signals the body's blood cells to weaken or dilate a bit so white blood cells and other protective substances can slip through easier and fight the foreign invader. In that case, in terms of a histamine response to a virus like COVID-19, it's possible that the body could produce enough histamine to mimic an allergic reaction in addition to fighting off the virus.

Histamines are also known as signaling molecules, which means they send messages between cells, according to MedlinePlus, a resource from the US National Library of Medicine. For example, one of those messages includes ensuring that stomach cells produce stomach acid. "Histamine is part of the immune response and, even though people colloquially associate it with allergies, it has several other roles," infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, told Health.

Also, for what it's worth, anti-histamines—or medications used to tamp down a histamine response—are commonly given to people with the common cold and other viruses, including COVID-19, said Dr. Adalja. "Famotidine (Pepcid) is also an anti-histamine and being studied for use in COVID-19 patients because of the role of histamine with infection."

While, again, this specific response has not been commonly seen in COVID-19 patients, Dr. Adalja added that he also hadn't seen any COVID-19 patients with facial swelling or other symptoms that mimic allergic reactions. However, there is the rare possibility that you could have an allergic reaction to COVID-19 vaccines. As of February 2022, the CDC has provided information regarding what to do in cases of non-severe and severe allergic reactions to any of the COVID-19 vaccines.