Drug and Vaccine Allergies
If you have a drug or vaccine allergy, your immune system thinks a medication is harmful and mistakenly activates. This can cause an allergic reaction that’s mild, severe, or potentially life-threatening.
What are drug and vaccine allergies?
A drug allergy is a reaction to a medication that occurs when your immune system is incorrectly activated.
Most of the time, it causes mild symptoms such as a fever, hives, or a rash. But it can also cause serious reactions, and rarely, anaphylaxis (a life-threatening reaction).
All drugs can cause allergic reactions, including penicillins and other antibiotics, non-steroidal anti-inflammatory drugs (such as aspirin or ibuprofen), and local and general anaesthetics.
It’s very rare to have an allergic reaction to a vaccine. When it does happen, it isn’t usually caused by an allergy to the active ingredient (the substance that makes the medicine work) in the drug, but by an excipient (other ingredients that make up the medicine).
Allergic reactions aren’t the same as side effects, which are known potential reactions that are detailed on the medication’s label.
Our specialist allergists see patients with drug and vaccine allergies in our Allergy centre, where they offer the most advanced care and treatment.
More information
Common, milder, and usually less serious symptoms of allergic reactions may occur within hours of taking the drug. These might include:
skin rashes, including hives (a raised, itchy rash)
skin swellings
itchy skin
a runny nose
itchy and/or watery eyes
shortness of breath
wheezing
dizziness
fever
Drug anaphylaxis is a rare but life-threatening reaction to a drug. Symptoms include:
tightening of the airways and throat
difficulties breathing
nausea
stomach cramps
vomiting
diarrhoea
seizure
dizziness and/or lightheadedness
a drop in blood pressure
loss of consciousness
cardiac arrest
death
If you have a serious reaction or the symptoms of anaphylaxis, seek emergency medical help immediately.
Allergic reactions to a drug or vaccine occur when your immune system mistakenly thinks it’s a harmful substance. Your immune system then creates an antibody (a blood protein) to counteract it. Chemicals are released in an attempt to attack the substance, and these cause the symptoms of an allergic reaction.
It doesn’t always happen the first time you take a drug, though. Sometimes, it only happens after several exposures to that specific medicine.
For some slower reactions that mainly impact your skin, it’s thought that your T-cells (a type of white blood cell) may cause the reaction. They’re believed to identify some drugs as harmful and bind themselves to them.
Risk factors
You may have a higher chance of experiencing a drug or vaccine allergy if:
you or a family member has a history of drug or vaccine allergies
you have food allergies, hay fever, or other allergies
you take high doses of a medication for a long time
you have HIV
you have Epstein-Barr virus (EBV) infection
If you suspect you may have a drug or vaccine allergy, you’ll meet your consultant for an initial consultation.
During the appointment, they’ll ask you about your medical and family history and your symptoms. They’ll likely also need to run some tests to make a diagnosis. These may include skin prick and intradermal tests with the relevant drugs, blood tests, and a drug provocation test where you’re given a small amount of the suspect drug under medical supervision.
The results of these tests will help your consultant to make an accurate diagnosis and recommend the most appropriate and effective treatment for you.
If you have a drug or vaccine allergy, you can prevent allergic reactions by avoiding that particular medication.
It’s also important to tell any medical professional that you come into contact with, including your GP or dentist, so that your allergy is noted down on your medical record.
Some people also wear a medical alert bracelet or necklace that identifies their allergies in case of medical emergencies. You can also make a note of your allergy, laminate it, and carry it with you at all times.
The majority of allergic reactions to drugs and vaccines are mild and involve common symptoms. However, like with all medications, there’s a risk of serious reactions or anaphylaxis, which can be life-threatening if it isn’t treated immediately.
There’s also a low chance of developing other conditions as a result of a drug or vaccine allergy. These complications are less common and include:
anaemia
nephritis (inflammation in your kidneys)
serum sickness
drug rash with eosinophilia and systemic symptoms (DRESS)
Your consultant will talk you through your treatment options once they’ve made a diagnosis and identified which drug or drugs you’re allergic to.
Initial treatment of a mild drug or vaccine allergy usually involves you stopping taking that suspected drug and focusing on relieving your symptoms with antihistamines and corticosteroids.
In severe cases, including anaphylaxis, you may be given an injection of adrenaline. If your allergy is severe and you’re at risk of anaphylaxis, you may be prescribed an epinephrine auto-injector to use if you experience another reaction.
Going forward, if you need to continue taking a drug that you’re allergic to, you may be recommended a treatment called drug desensitisation or allergy immunotherapy. You’ll be given increasingly larger doses of the drug over the course of hours or days. Your immune system may start to build a tolerance against the drug. If you don’t have an allergic reaction, you may be able to continue taking the drug.
At Welbeck, our allergists are experts in their field and are dedicated to providing world-class care to every patient.
With access to colleagues across other specialties, our consultants are also able to refer within the Welbeck ecosystem if required to ensure you receive the treatment you need as quickly as possible, all under one roof.
All appointments, testing, treatment, and follow-up appointments take place within our state-of-the-art facilities, enabling us to deliver accurate diagnostics and advanced treatments.
Your health is important to us, so we strive to offer same-day appointments whenever possible.
Our consultants are recognised by the major health insurance companies. If you have private health insurance, your treatment at Welbeck can begin once you have obtained authorisation. We also provide care to self-paying patients. Learn more about the different payment options at Welbeck.
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Frequently asked questions
Around 10% of the population is thought to be allergic to penicillin, which is prescribed to treat bacterial infections. For most people, their reaction is mild to moderate.
If your reaction is mild, your symptoms should ease a few hours after you stop taking the drug. However, some people may find it takes longer — sometimes weeks or months — to recover.
Hives can look like raised bumps that appear in patches on 1 or many areas of your body. They can look pink or red if you have white skin, but they can be harder to spot if you have brown or black skin.
Stress and anxiety may exacerbate your symptoms during an allergic reaction. This is mostly down to emotional stress. However, researchers also believe stress can make your immune system react more strongly, too.