True drug allergies, which involve the body's immune system and histamine release, account for 6 to 10 percent of all adverse drug reactions, according to the American Academy of Allergy, Asthma and Immunology, AAAAI. In contrast to local skin and digestive reactions, true drug allergies range from itchy skin rashes, called hives, to breathing emergencies like anaphylaxis. Certain types of antibiotics and anticonvulsants are most often associated with these drug allergies.
Penicillin Antibiotics
Penicillin, the first drug designed to treat bacterial infections, is also the most common cause of drug-related anaphylaxis, according to the AAAAI. People who develop an immune system reaction to penicillin are also allergic to related antibiotics. For example, amoxicillin, ampicillin and methicillin contain the same allergy-inducing chemical ring structure as penicillin. Other antibiotic drugs, such as cephalexin, cause cross-reacting drug allergies in some individuals as well.
Sulfa Drugs
Sulfamethoxazole is a sulfonamide antibiotic that causes an immune system reaction toward the sulfa part of the drug. Because of the sulfa similarity, non-antibiotic drugs, such as sulfasalazine, also cause an allergic reaction. People with allergies to sulfa drugs may experience allergic reactions to diabetes treatments and diuretic drugs. Although mild allergic reactions are more common with sulfa drugs, a severe allergic reaction called Stevens-Johnson Syndrome, SJS, also occurs with sulfa drugs. SJS causes tongue swelling, skin shedding and purple, blistering skin rashes that may lead to permanent damage.
Anticonvulsant Drugs
Anticonvulsant, such as phenytoin and carbamazepine, prevent seizures but also cause anticonvulsant hypersensitivity syndrome, a type of allergic reaction. People allergic to anticonvulsants experience skin rashes called erythema multiforme that may damage internal tissues as one of the triad of hypersensitivity symptoms. High levels of liver enzymes and of eosinophils, which are cells that increase allergic responses, complete the symptom triad.
References
- American Academy of Allergy, Asthma and Immunology: Allergy Statistics
- The New York Times Health: Drug Allergy Overview
- "Anticonvulsant drug hypersensitivity": Galindo PA, Borja J, Gómez E; 2002
- MayoClinic: Sulfa Allergy
