© Shutterstock

Allergy or side effect? -

Many medications have side effects, but these are not necessarily allergic reactions. Common side effects may include headaches, nausea, and constipation.

© Shutterstock

Allergy or side effect? -

Allergies occur when the immune system perceives a substance as a threat and attacks it, causing a number of bodily reactions. These can range from rashes and hives to anaphylaxis (which can be fatal).

© Shutterstock

Penicillin -

Penicillin is a popular antibiotic, and indeed one that had a huge impact in how bacterial infections are treated since it was first discovered in the 1920s.

© Shutterstock

Penicillin -

But penicillin, and other penicillin-related drugs, can cause an allergic reaction. Hives, rashes, and itching are some of the most common symptoms.

© Shutterstock

Penicillin -

Medications that can cause such a reaction include ampicillin, amoxicillin, amoxicillin-clavulanate (Augmentin), and cephalosporins (e.g. cephalexin and ceftriaxone).

© Shutterstock

Nonsteroidal anti-inflammatory drugs (NSAIDs) -

NSAIDs are very popular, and many are sold over-the-counter. These drugs include aspirin, ibuprofen (e.g. Advil), naproxen (e.g. Aleve), diclofenac (e.g. Voltaren), indomethacin, ketorolac, and meloxicam.

© Shutterstock

Nonsteroidal anti-inflammatory drugs (NSAIDs) -

These medications are often used to reduce inflammation and as painkillers. Prolonged use can, however, lead to a number of side effects, including stomach ulcers.

© Shutterstock

Nonsteroidal anti-inflammatory drugs (NSAIDs) -

While generally these medications are well tolerated by most, a small percentage of people may experience NSAID-induced hypersensitivity reactions (NHRs). These reactions are still pretty rare, and those with chronic respiratory and skin conditions are more likely to have them.

© Shutterstock

Corticosteroids -

Corticosteroids, aka steroids, are used to treat a number of conditions, and are popular choices when it comes to reducing inflammation and suppressing the immune system. These drugs include cortisone, hydrocortisone, methylprednisolone, and prednisone.

© Shutterstock

Corticosteroids -

While these are often used in the treatment of allergies, paradoxically, they can also be the cause of allergies. For instance, contact dermatitis can sometimes occur when topical corticosteroids are used. Allergic reactions to corticosteroids in general, however, are not very frequent.

© Shutterstock

Sulfonamides -

These groups of drugs, also known as sulfa drugs, have mostly an antibacterial action (antibiotics), but there are also some used as anti-diabetes drugs and anticonvulsants.

© Shutterstock

Sulfonamides -

Popular medications include antibiotics (sold under brand names such as Bactrim and Eryzole), anti-diabetes drugs such as Diabeta, sulfasalazine, dapsone, sumatriptan, celecoxib, and hydrochlorothiazide.

© Shutterstock

Sulfonamides -

People who have allergic reactions to sulfonamides can experience skin rashes and sometimes anaphylaxis. A rare and severe allergic reaction includes the development of Stevens-Johnson syndrome, which causes painful blisters on several parts of the body. A trip to the ER is required in such cases.

© Shutterstock

Anti-seizure medications -

These medications are not only used to manage seizures, but they are also commonly prescribed to treat other conditions, including anxiety, nerve pain, and Parkinson's disease. Examples include phenytoin, valproic acid, gabapentin, and benzodiazepines (e.g. diazepam).

© Shutterstock

Anti-seizure medications -

Also known as anticonvulsants or anti-epileptic drugs, these medications can trigger anticonvulsant hypersensitivity syndrome (AHS). Although rare, it can be very serious. Symptoms include fever, rashes, and even organ damage. Unlike a typical allergic reaction, people with AHS tend to develop symptoms somewhere between two weeks to two months after taking the medication.

© Shutterstock

Medications for autoimmune conditions -

Drugs used to treat autoimmune conditions contain antibodies called monoclonal antibodies, which are attached to proteins called antigens.

© Shutterstock

Medications for autoimmune conditions -

Such drugs are commonly used to treat conditions such as rheumatoid arthritis, psoriasis, lupus, and inflammatory bowel disease. These drugs are also used in the treatment of other diseases, including cancer and COVID-19.

© Shutterstock

Medications for autoimmune conditions -

Allergic reactions to monoclonal antibodies such as trastuzumab (Herceptin), dupilumab (Dupixent), pembrolizumab (Keytruda), and ocrelizumab (Ocrevus) have been reported. The severity of symptoms varies, depending on the person. These can occur shortly after taking the drugs, or manifest a few days later.

© Shutterstock

Insulin -

Insulin was a game changer in the treatment of diabetes when it was first extracted in the 1920s.

© Shutterstock

Insulin -

Insulin is mostly used by people with type-1 diabetes, who inject the hormone. As such, irritation at the site where insulin is injected can occur. But the hormone can also cause other, more serious allergic reactions, including anaphylaxis.

© Shutterstock

Chemotherapy drugs -

The drugs used in the treatment and management of cancer are classified in a number of ways, depending on their action. These include alkylating agents (e.g. cyclophosphamide and busulfan), antitumor antibiotics (e.g. bleomycin), anti-metabolites (e.g. methotrexate), and plant alkaloids (e.g. mitomycin).

© Shutterstock

Chemotherapy drugs -

Despite the many side effects of these drugs, allergic reactions are quite rare, but can occur. In such cases, antihistamines and steroids may have to be taken so that patients can undergo treatment.

© Shutterstock

Medications for HIV -

HIV (human immunodeficiency virus) requires treatment so that it won't develop into the later stage of the disease—AIDS (acquired immunodeficiency syndrome). To do so, patients undergo antiretroviral treatment, or ART.

© Shutterstock

Medications for HIV -

Some people may have an allergic reaction to ART, even though HIV affects the immune system, so people with the virus are less likely to develop allergies due to the weakened immune response.

© Shutterstock

Muscle relaxants -

These medications block the pain signals that trigger a muscular contraction. These are commonly used in the treatment of spasms and muscle pain, triggered by conditions such as fibromyalgia, multiple sclerosis, and Parkinson's disease. These medications include baclofen, cyclobenzaprine, dantrolene, tizanidine, and methocarbamol.

© Shutterstock

Muscle relaxants -

These drugs are also used in anesthesia, more specifically neuromuscular blocking agents (NMBAs) that prevent muscles from moving during surgery. NMBAs can, however, trigger a serious allergic reaction, i.e. anaphylaxis. An anesthesiologist plays a vital role in such cases.

© Shutterstock

Contrast dyes -

Not a medication as such, but contrast dyes are used in medical imaging such as X-rays, CT scans, ultrasounds, and MRIs, to have a clearer image of some body parts. The composition of contrast dyes varies, and can include iodine, barium sulfate, gadolinium, and salt water.

© Shutterstock

Contrast dyes -

Allergic reactions may include hives, difficulty breathing, swelling, nausea, and vomiting. Being allergic to one type of contrast dye, however, doesn’t necessarily mean that the person is allergic to all types of contrast dyes.

© Shutterstock

Barbiturates -

Barbiturates are not as popular today as they used to be, particularly because they can cause severe sedation and be very addictive. These drugs are, however, still used to treat insomnia and seizures in some cases.

© Shutterstock

Barbiturates -

Allergic reactions to barbiturates can range from mild (e.g. skin rash) to severe (e.g. Stevens-Johnson syndrome, anaphylaxis, and toxic epidermal necrolysis).

Sources: (CDC) (Health Digest) (Healthline) (FDA) (Mayo Clinic) (MedicineNet) (StatPearls) 

See also: Allergy or intolerance? Most adults have it wrong

© Shutterstock