Health Tips

Can someone with a history of allergies, particularly allergies to drugs/medications, receive the Covid-19 vaccine? What are medication allergies, anyway? How can you tell if you really have allergies to medications?

Yes, it is. Because people may understand allergies differently and as a result, mistaken something else as an allergy, when in reality it may not be.

Fret not, in this article, we will give you a broad understanding about medication allergies and illuminate you on the question of the day: should you receive a Covid-19 vaccine if you have a drug allergy?

What is a drug allergy?

P.S. By drug we mean the medication, whether it’s prescribed by your doctor or over-the-counter medication. 

A drug allergy, also called drug hypersensitivity, is a bad reaction to a drug that happens when the body's immune system responds to a drug as if it were a dangerous invader and tries to fight it off. The job of the immune system is to fight off infection. Normally, it should not react to a drug as though it were an invader, but some drugs can cause that response in some people.

A drug allergy is not the same as a drug side effect. Side effects are unintended or unwanted effects that drugs can cause. Side effects can affect anyone who is given enough of a drug. Drug allergies, on the other hand, affect only a small number of people.

Not all drug allergies are the same

The World Allergy Organization (WAO) (yes we have a worldwide organization for allergies) recommends that when we talk about drug allergies, we can categorize them into two types:

• Immediate reactions, occurring within one hour of the first administered dose of drug

• Delayed reactions, occurring after one hour but usually more than six hours and occasionally weeks to months after the start of administration of the drug

Immediate reactions

This type of allergy starts quickly after a drug is taken (usually within an hour or so). It usually happens with drugs that a person had taken before without any problem. Symptoms can include:

• Hives, which are raised, red patches of skin that are usually very itchy 

• Itchy skin

• Flushing, which is when your skin turns red and feels hot

• Swelling of the face, hands, feet, or throat (angioedema)

• Throat tightness, hoarse voice, wheezing, or trouble breathing

• Nausea, vomiting, belly pain

• Feeling lightheaded

Hives or urticaria. Image credit: Allergy Research, CC BY-SA 4.0, via Wikimedia Commons

Angioedema. Image credit: ^©DermNet New Zealand via CC BY-NC-ND 3.0 NZ

This is why Health director-general Tan Sri Dr Noor Hisham Abdullah said that there will be a recovery bay where all those who have been vaccinated will be observed for 30 minutes. This 30-minute window is what allows the doctors to treat you immediately should you develop a serious form of immediate allergic reaction called anaphylaxis following Covid-19 vaccination. 

Anaphylaxis

Anaphylaxis is a severe and potentially life-threatening reaction to a trigger such as a drug allergy. It can also happen with other triggers such as food. Anaphylaxis usually develops suddenly and gets worse very quickly. The symptoms include:

• feeling lightheaded or faint

• breathing difficulties – such as fast, shallow breathing

• wheezing

• a fast heartbeat

• clammy skin

• confusion and anxiety

• collapsing or losing consciousness

;in addition to the symptoms mentioned above. Death is often due to obstruction to breathing or extreme low blood pressure, called anaphylactic shock. 

The treatment of anaphylaxis is to inject the person with an adrenaline (also called epinephrine) auto-injector into the person’s muscles. A person with a known history of anaphylaxis usually carries around an adrenaline auto-injector in case the condition occurs. 

EpiPen epinephrine dispensing device. Image credit: Sean William, CC BY-SA 3.0 via Wikimedia Commons. 

Nonetheless, anaphylaxis is a medical emergency; if you think someone is experiencing anaphylaxis, it’s best to call 999 for an ambulance immediately, even if the person starts to feel better.

Delayed reactions

A delayed drug allergy is much more common. It is not very serious and usually causes a rash that begins after a few days (and occasionally weeks to months) of taking a drug. The rash often spreads over much of the skin. Sometimes it is itchy, but sometimes not. 

This type of drug allergy does not involve swelling, trouble breathing, throat tightness, or the other symptoms listed above. It doesn't usually get worse or affect anything besides the skin. In very rare cases, such delayed allergy may result in a very severe condition called Stevens-Johnson syndrome and toxic epidermal necrolysis, or SJS/TEN, in short. It involves skin peeling, fever, body aches, red rashes and blisters all over the skin. 

Drug pseudoallergy

This is an interesting one. The word ‘pseudo’ means fake, so does that mean that drug pseudoallergy is a ‘fake’ reaction?

Well, not quite. A drug pseudoallergy is a reaction that invokes similar symptoms as the drug allergies we mentioned above (called true drug allergy), but it is not caused by the immune system. The term "non immune-mediated hypersensitivity" is also used. Drug pseudoallergy, such as those to nonsteroidal anti-inflammatory drugs (NSAIDs), can be as severe as the drug allergies caused by the immune system and are treated in the same manner.

Other classifications

Healthcare professionals also use another classification system to identify drug allergies. It is called the Gell and Coombs system which goes like this:

• Type I – Immediate in onset and caused by immunoglobulin (Ig)E-mediated activation of mast cells and basophils

• Type II – Delayed in onset and caused by antibody (usually IgG-mediated) cell destruction

• Type III – Delayed in onset and caused by immune complex (IgG:drug) deposition and complement activation

• Type IV – Delayed in onset and T cell-mediated

So many jargons, we know. Just understand that this classification is important for healthcare professionals to determine appropriate diagnostic procedures, options for further treatment, and possible allergies with similar medications.

Will I need tests to find out if I REALLY have drug allergy?

The answer is: maybe. If your doctor suspects you have an immediate reaction, he or she might do allergy tests. The most common type of testing is called skin testing. For this test, the doctor puts a drop of the drug you might be allergic to on your skin and makes a tiny prick in your skin, or injects a very tiny amount. He or she then watches your skin to see if it turns red and bumpy.

Say if you do have a possible allergy that consists only of a rash (the type that is not serious), your doctor might want to do a "drug challenge test." For this test, the doctor will have you take a small amount of the drug that caused the rash while he or she observes you. That way the doctor can find out if you will have the same reaction twice. Doctors usually do drug challenge tests only with certain medicines that are used a lot and can't easily be replaced with a different medicine. For example, the antibiotic amoxicillin is the best choice of antibiotic for many common infections. Because of this, it's important that people only avoid it if they are truly allergic to the drug class penicillins.

Should I receive Covid-19 vaccine if I have a drug allergy?

Photo by National Cancer Institute on Unsplash

It depends. According to the United States Centers for Disease Control and Prevention (CDC), you should not get an mRNA Covid-19 vaccine (which is produced by Pfizer-BioNTech and Moderna) if you are allergic to polyethylene glycol (PEG) or polysorbate, regardless of the severity of allergies. PEG is one of the ingredients in mRNA Covid-19 vaccine, polysorbate is not but it is closely related to PEG. 

On the other hand, if you have a history of allergic reactions, severe or not, to:

• Food

• Pet

• Venom

• Environmental factors

• Latex

• Oral medications 

CDC says that you should get vaccinated. If you are allergic to other types of vaccines, CDC recommends that you ask your doctor if you should get a Covid-19 vaccine. 

What to do if I have an allergic reaction AFTER receiving the first shot of Covid-19 vaccine

Most Covid-19 vaccines, including the one produced by Pfizer-BioNTech, require two doses. If you develop an allergic reaction after receiving the first dose of Covid-19 vaccine, the CDC recommends that you should not get the second dose.

CDC has learned of reports that some people have experienced a red, itchy, swollen, or painful rash where they got the shot. These rashes can start a few days to more than a week after the first dose and are sometimes quite large. These rashes are also known as “COVID arm.”, and so far has only been reported with individuals receiving mRNA vaccine from Moderna, which Malaysia has no plan to purchase as of now.

If you experience “COVID arm” after getting the first shot, you should still get the second shot at the recommended interval. Tell your vaccine provider that you experienced COVID arm after the first shot. Your vaccine provider may recommend that you get the second shot in the opposite arm.

Allergies to Covid-19 vaccine is rare 

During December 14–23, 2020, the Vaccine Adverse Event Reporting System has detected only 21 cases of anaphylaxis after administration of a reported 1,893,360 first doses of the Pfizer-BioNTech COVID-19 vaccine. That is 11.1 cases per million doses, a very low number of allergic cases to be worrying! If it is any assurance, 71% of these occurred within 15 minutes of vaccination, which means even in the worst case scenario, doctors at the site of vaccination can offer treatment to you immediately. 

Remember, nobody is safe until everyone is safe. We need at least 80% of the adult population vaccinated to achieve herd immunity, and that would be impossible if everyone of us refused to play our part by getting vaccinated. #LindungDiriLindungSemua

A word from Doc2Us

If you are still hesitant about getting vaccinated against Covid-19, we hope this article can change your mind. Want to speak to a healthcare professional about Covid-19?  We highly welcome you to consult our Covid-19 Task Force, which consists of professional doctors and healthcare professionals, for FREE! 

You can access to free Covid-19 virtual health advisory by downloading the Doc2Us app on http://onelink.to/doc2us or use our web chat https://web.doc2us.com/

For more information about Covid-19 vaccination programme in Malaysia, visit https://www.vaksincovid.gov.my/

Disclaimer: COVID-19 is a novel disease. The information and scientific evidence of its development and vaccines are changing as we speak. Some content of this article may be outdated in the future. We encourage you to always speak with a healthcare professional you trust for the latest updates on COVID-19 and its vaccines.

References

1. UpToDate - Drug hypersensitivity: Classification and clinical features

2. UpToDate - An approach to the patient with drug allergy

3. UpToDate - Patient education: Drug allergy (The Basics)

4. DermNet NZ - Allergies explained

Cover image credit: Photo by National Cancer Institute on Unsplash

Written by

Ms Joyce Toh