The signs and symptoms of a penicillin allergy may range from mild to severe. Several of the common signs and symptoms of an allergic reaction to penicillin are not life–threatening. Still, people experiencing any of these symptoms after taking penicillin should consult a physician. The physician should be able to prescribe an alternate medication. Common symptoms include a rash, hives, itchy eyes and angioedema (swelling of the tongue, lips or face).

Some individuals may experience more severe reactions to taking penicillin. Anaphylaxis is a rare, severe allergic reaction that involves two or more body systems. It often begins immediately after an individual has been exposed to a particular allergen. Signs of an anaphylactic reaction include:

• Dizziness
• Increased thirst
• Increased weakness or tiredness
• Weight loss
• Wheezing
• Faster or slower pulse
• Blue skin, lips or fingernail beds (cyanosis)
• Nausea or vomiting
• Diarrhea
• Seizures
• Unusual bleeding or bruising

The most sensitive individuals may experience a potentially life–threatening condition called anaphylactic shock, which usually involves the constriction of the air passageways and a dangerous drop in blood pressure. Symptoms include:

• Shortness of breath
• Tightening in the chest or throat
• Choking
• Loss of consciousness

Individuals who exhibit signs of anaphylaxis or anaphylactic shock should seek immediate medical help.

Because penicillin is used to treat infection, and a common symptom of infection is a rash, many people mistakenly believe they have an allergy to penicillin when a rash develops after a shot. Common drug side effects, such as nausea, can also be misperceived as signs of an allergy. Unlike drug allergies, drug side effects do not involve an immune system reaction.

Individuals who suspect a penicillin allergy for any reason should consult a physician. A physician can perform a skin test or other tests to diagnose whether a penicillin allergy is present or not.

Certain types of penicillin are known to cause dark or amber urine, pale stools, stomach pain or yellow eyes and skin (jaundice). These include amoxicillin, clavulanate, azlocillin, mezlocillin, oxacillin and piperacillin. Though these signs and symptoms do not indicate the presence of an allergy, they may signal the presence of a liver disorder, and therefore should be reported to a physician.