Almost all drugs elicit certain adverse reactions from people who are hypersensitive to it. Allergies account for around 10% of adverse drug reactions especially with antibiotics. In many cases, penicillin and amoxicillin are the leading causes of antibiotic allergy.

Mechanism of the reaction

Antibiotics can bring about symptoms ranging from a localized rash to a full-scale urticaria, swelling, and problems in breathing which may greatly affect vital systems. This is the real problem with antibiotic allergy—the risk for developing anaphylactic shock. In the United States, more than 400 deaths per year are attributed to anaphylaxis secondary to penicillin alone.

Under normal conditions, penicillin itself is not capable of stimulating an immune response against it. However when metabolized, its by-product, benzylpenicilloyl, can bind with tissue proteins which makes it immunogenic, stimulating production of antibodies and cellular reactions against the drug. An allergic reaction occurs when the body induces an inflammatory response to counter the foreign agent, which in this case, is an antibiotic (penicillin). But, this does not happen on the body’s first encounter with the medication. The allergic reaction will most likely occur on the succeeding time a sensitized person will take the medicine wherein his body has already produced enough antibodies to cause the reaction. Typical manifestations include:

• blotchy rashes
• hives
• angioedema (swelling of the tissue beneath the skin)
• coughing
• wheezing

Anaphylaxis may follow but only in rare cases of severe allergic reaction. Symptoms include difficulty of breathing, narrowing of the air passages, abdominal pain, nausea and vomiting, sudden drop in blood pressure, and loss of consciousness.

What your Doctor can do for you

Nowadays, in the clinical setting, it is a standard operating procedure that a skin testing must be performed before the administration of any antibiotics. Rarely, a challenge test may be performed. In the event that the person is truly allergic to penicillin, the current drug is discontinued and a different class may be given. Epinephrine is given to open up the airways in case of anaphylaxis. Supportive treatment may include antihistamines and corticosteroids. Desensitization may be suggested upon thorough evaluation of the individual’s condition.

What you can do

From the diagnosis of your condition, you are advised to avoid the intake of the specific drug that you are allergic with. Some people who have experienced severe reactions are given with epinephrine kit that they should always carry with them. A person may be asked to wear a medic-alert bracelet as necessary, or simply tell the health team the drugs that you are allergic to. Minor symptoms such as itching and rashes can be soothed with calamine lotion or a cool shower.   As soon as you experience the initial symptom (rash), take your prescribed medicine such as antihistamine to prevent further symptoms.