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Antihistamines for COVID-19: Can Benadryl or Zyrtec Help With Symptoms?

Medically reviewed by Manuel Penton, M.D.
Posted on August 22, 2023

If you’re looking through your medicine cabinet for a remedy to help with COVID-19 symptoms, you might find an antihistamine for allergies and wonder if it can help.

The Centers for Disease Control and Prevention (CDC) recommends over-the-counter (OTC) pain relievers, such as acetaminophen (Tylenol) or ibuprofen (Motrin or Advil), to manage COVID-19 symptoms at home, but they don’t mention antihistamines.

Continue reading to find out if an antihistamine can help relieve your COVID-19 symptoms.

What Are Antihistamines?

Antihistamines are medications that are typically used to temporarily relieve symptoms associated with allergies, allergic reactions, and asthma, such as:

  • Allergic rhinitis (hay fever)
  • Itchy or watery eyes
  • Rashes like hives
  • Nasal congestion
  • Nausea or vomiting

How Do Antihistamines Work?

Antihistamines block the effect of a chemical called histamine. Immune cells called mast cells usually release histamine in response to something harmful, like a type of bacteria or virus. Histamine helps regulate inflammation and several body functions.

Antihistamines are classified based on which type of histamine receptor they block — H-1 or H-2. Histamine connects to these receptors to trigger an effect in the body. H-1 receptors can be found all over your body, including in your blood vessels, airways, and brain. H-2 receptors are mostly found in your stomach.

When histamine activates H-1 receptors, it helps fight the foreign invader by triggering several events, including expanding blood vessels and turning on other immune cells. Histamine can also use H-1 receptors to release proteins called cytokines that increase inflammation.

Activating the H-1 receptor can also trigger a number of symptoms, such as:

  • Redness
  • Faster heartbeat
  • Itchiness
  • Pain

These reactions are normal and helpful when your body is fighting a foreign invader, like a virus or bacteria. However, in people with allergies, histamine is released in response to a substance that isn’t harmful, like pollen or pet dander.

When people refer to antihistamines, they’re usually referring to H-1 blockers — also known as H-1 receptor antagonists — to treat allergy and asthma symptoms. H-2 receptor blockers such as famotidine (Pepcid) are commonly used to treat digestive tract issues, such as heartburn.

Types of Antihistamines

Two main types of antihistamines work on H-1 receptors — first-generation and second-generation antihistamines.

The main difference between these two types is that first-generation antihistamines can affect the histamine receptors in your brain and result in drowsiness. Second-generation antihistamines don’t cross into the brain as much, so they’re usually considered nondrowsy drugs.

Many antihistamines are available over the counter, but some require a prescription. Examples of first-generation OTC antihistamines include:

  • Diphenhydramine (Benadryl)
  • Chlorpheniramine (Chlor-Trimeton)
  • Doxylamine (Unisom, Vicks Nyquil)

Second-generation OTC antihistamines include:

  • Loratadine (Claritin)
  • Cetirizine (Zyrtec)
  • Fexofenadine (Allegra)
  • Desloratadine (Clarinex)

What Are the Symptoms of COVID-19?

The symptoms of COVID-19 differ among individuals. You may experience a few, many, or none of the possible symptoms. They can range from mild to severe — anyone can have severe symptoms.

Possible symptoms include:

  • Fever
  • Chills
  • Trouble breathing
  • Extreme tiredness
  • Muscle aches
  • Headache
  • Loss of taste or smell
  • Nasal congestion
  • Runny nose
  • Nausea
  • Vomiting
  • Diarrhea

You might notice that several of these symptoms overlap with those of allergies that antihistamines can treat. In fact, having allergies can feel a lot like being sick. However, when you have COVID-19, your symptoms are caused by a virus instead of your body’s response to allergens like pollen.

How Might Antihistamines Help With COVID-19 Symptoms?

COVID-19 is caused by a virus. In response to a viral infection, your body can trigger your immune cells to release histamine, causing inflammation and respiratory symptoms. Antihistamines can block these effects.

In addition to improving common symptoms of COVID-19, antihistamines might help prevent or treat a more serious symptom called cytokine release syndrome — also known as cytokine storm. This condition can happen when your body overreacts to fighting COVID-19 and releases too many cytokines, which can cause more severe illness and organ damage.

Researchers think that taking an antihistamine might keep mast cells from releasing histamine during COVID-19. This could help because histamine is one of the signals your body uses to tell the immune system to release cytokines. Studies also suggest that certain antihistamines can decrease cytokine production.

Antihistamines may also reduce the risk of hospitalization in people regardless of their age or other existing medical conditions.

While some limited research suggests there could be a benefit of using antihistamines for COVID-19, the CDC and other health organizations don’t universally recommend these medicines. More research is likely needed to confirm if and how antihistamines could help with COVID-19. In the meantime, if you have been diagnosed with COVID-19, talk to your doctor about the best way to treat your symptoms and prevent serious complications.

Is One Antihistamine Better Than Others?

No evidence suggests that one antihistamine works better than others for the effects of COVID-19 that resemble allergy symptoms. Scientists have considered both first- and second-generation antihistamines for possible benefits in treating COVID-19, but more studies are necessary for experts to determine if one antihistamine would be more effective than others in this scenario.

In general, the specific side effects and drug interactions may make one antihistamine a better choice for you than others. Second-generation antihistamines are usually considered safer than first-generation antihistamines because they have fewer side effects and drug interactions.

Antihistamine Side Effects

Side effects are more common in first-generation antihistamines because they affect the H-1 receptors in your brain. The side effects of first-generation antihistamines include:

  • Drowsiness
  • Dizziness
  • Dry mouth
  • Headache
  • Increased heart rate
  • Difficulty urinating
  • Constipation

The side effects of second-generation antihistamines are usually milder because they don’t affect the brain’s H-1 receptors. Drowsiness, especially, is much less common in people taking a second-generation antihistamine. Possible side effects include:

  • Fatigue
  • Cough
  • Headache
  • Belly pain
  • Sore throat

Antihistamine Warnings

Although many antihistamines are available over the counter, they may not be safe for everyone. Be sure to check with a doctor if you are older than 65, may be pregnant, are breastfeeding, or are thinking of giving these drugs to a child. Also, people who have certain medical conditions may not be able to take antihistamines. Talk to your doctor before taking antihistamines if you have:

  • Kidney or liver problems
  • Heart disease
  • High blood pressure
  • Epilepsy

Some antihistamines can cause drowsiness and reduce your reaction speed and coordination. You shouldn’t drive or operate heavy machinery when taking these medications. Drowsiness and dizziness may also increase the risk of falling, especially in older adults.

Antihistamines can interact with some medications. In general, first-generation antihistamines have more drug interactions than second-generation antihistamines. Before taking an antihistamine, talk to your doctor or pharmacist to see if it might interact with your other medications. If your doctor suggests trying an antihistamine to help with your COVID-19 symptoms, they should give you instructions about which one to take, how much to take, and how often.

Talk With Others Who Understand

On myCOVIDteam, the online social network for people with COVID-19 and their loved ones, more than 8,000 members come together to ask questions, give advice, and share their stories with others who understand life with COVID-19.

Have you taken antihistamines to help your COVID-19 symptoms? Did they help? Share your experience in the comments below, or start a conversation by posting on your Activities page.

Posted on August 22, 2023

A myCOVIDteam Member

My GP put me onto loretadine since saturday and last night I was really so tired and today I am so spaced out. My BP is high and I was trying to fathom out why, thanks this articl had informed me it… read more

posted August 29, 2023
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Manuel Penton, M.D. is a medical editor at MyHealthTeam. Learn more about him here.
Amanda Jacot, PharmD earned a Bachelor of Science in biology from the University of Texas at Austin in 2009 and a Doctor of Pharmacy from the University of Texas College of Pharmacy in 2014. Learn more about her here.

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