Drug allergies cause a person’s immune system to react adversely to the presence of certain drugs in the body. They are different from a side effect, which does not involve an immune system reaction.  Most drug allergies cause symptoms that are mild, such as a small rash or other irritation. However, in rare cases – such as anaphylaxis – reactions can be life-threatening. As a result, an individual with drug allergies must take them seriously and seek medical attention when they suspect a reaction.

The most common drug allergies include:

• Penicillin and other antibiotic allergies. Antibiotics are the most common source of drug allergies.
  
  
• Serum sickness. A delayed allergic reaction that can occur a week or more after exposure to a medicine or vaccine.

Other drugs commonly known to trigger allergies include:

• Painkillers (e.g., aspirin, NSAID, codeine)
• Sulfa drugs
• Barbiturates
• Anticonvulsants
• Insulin drugs
• Local anesthetics (e.g., procaine)
• Iodine

Mild cases of drug-associated allergic reactions often can be treated with antihistamines or topical corticosteroids. However, an immediate injection of epinephrine is the only way to adequately treat the life-threatening reaction associated with anaphylactic shock.