Last week, someone asked a great question in the comments about drug allergies. Brilliant topic! It’s so misunderstood, and has a really important impact on your health.
What are some top things you should know about drug allergies? They are different from drug side effects.
Why do drug allergies matter?
- Drug allergies have the potential to limit your treatment options, meaning you can’t always receive the best drug for your disease, symptoms, or infection. This is important because many patients are FALSELY labeled as allergic. In recent important studies, 80% of patients labelled as penicillin allergic were not at all allergic. (This includes patient reporting of allergies, as opposed to diagnosis of allergy.)
- Inappropriate use of antibiotics, as well as using more and different antibiotics, has led to a global crisis of resistant bugs, such as MRSE and VRE. Docs and patients both sticking to a community standard list of first line antibiotics whenever possible can help reduce this (like vaccines, good community health for everyone is both personal and public.)
So, today, let’s talk more about what’s an allergy? A drug allergy or “hypersensitivity” is when your body’s immune system responds to a drug as if it were a germ. The job of the immune system is to fight off infection, but when it over-reacts, it can cause a bad reaction.
An allergic reaction will happen almost immediately after taking the drug and can include itching, with or without hives, Flushing, which is when your skin turns red and feels hot, Swelling of the face, hands, feet, or throat, hoarseness, wheezing, or trouble breathing, or a drop in blood pressure
There is one type of late-onset drug allergy, which has led to confusion. Sometimes, a rash that begins after a few days of taking a drug. The rash isn’t always itchy, and there are NO other symptoms. Why is this confusing? Well, many diseases, infections, and ESPECIALLY viral illness can ALSO cause a non-specific red rash. So, your toddler got an ear infection and an antibiotic. A few days later, s/he had a red rash. Is it because the ear infection was viral, a type of harmless, non-specific rash we see with viruses call “viral exanthem” or drug allergy? It’s not always clear.
A drug allergy is NOT the same as a drug side effect.
Side effects are common, and include any unwanted effects that the drugs can cause. Side effects can affect anyone who is given enough of a drug.
So what do you do about an allergy? True immediate allergic reactions require ambulance and hospital. Ring 999.
Not sure about a drug allergy? Talk to your doctor. If it’s necessary, one option is allergy skin tests. A specialist doctor puts a drop of the drug you might be allergic to on your skin and makes a tiny prick in your skin, then watches for a skin reaction.
#pseudosciencesucks: Home allergy testing kits using hair/skin and blood tests of all sorts CANNOT diagnose a drug allergy. Full stop. [Honestly, if that worked, every doc would do that blood test in hospital. It would be amazing!]
If you have a reaction that consists only of a rash with no other symptoms, a doctor might suggest a “drug challenge test,” where you have a small dose of the drug that caused the rash while under medical observation. Docs usually only do drug challenge tests only with certain medicines that are common and don’t have good alternatives, where it would be better for your treatment options if you didn’t have to avoid something for no reason.
How is that different from drug side effects?
These are REALLY common. Basically, anytime a patient gets a symptom from a drug that is unwanted, it is a side effect.
What are among the commonest side effects mistaken for allergies? Tummy upsets from antibiotics or rashes/nausea/low blood pressure from opiates. It’s really important for your health, because there aren’t an endless amount of alternatives to antibiotics or pain killers, especially if you are seriously unwell.
What other side effects can drugs have? Almost anything, depending on the drug! And we know that for many reasons, some patients experience them more often or more intensely than other patients. Below, I list just some side effects and some of the commonest culprits.
- Nausea or vomiting is very common from pain killers and antibiotics.
- Dizziness is common from blood pressure tablets.
- Headache from certain medications for heart problems or erectile dysfunction.
- Upset stomach, diarrhoea, or constipation from many drugs, but commonly from antibiotics or painkillers.
- Feeling more or less hungry than usual, almost any drug. Steroids, classically, can make you very hungry
- Trouble sleeping – steroids can be the worst for this one.
- Dry mouth – many, many medications
- Dry cough that doesn’t go away – certain heart medications can cause this one
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