Symptoms:

• Anaphylaxis, or severe allergic reaction (see below)
• Hives (a less common type of rash)
• Itching of the skin or eyes (common)
• Skin rash (common)
• Swelling of the lips, tongue, or face
• Wheezing

Symptoms of anaphylaxis include:

• Abdominal pain or cramping
• Confusion
• Diarrhea
• Difficulty breathing with wheeze or hoarse voice
• Dizziness
• Fainting, light-headedness
• Hives over different parts of the body
• Nausea, vomiting
• Rapid pulse
• Sensation of feeling the heart beat (palpitations)

Signs and tests:

An examination of the skin and face may show hives, rash, or angioedema (swelling of the lips, face, or tongue). Decreased blood pressure, wheezing, and other signs may indicate an anaphylactic reaction.

Skin testing may confirm allergy to penicillin-type medications. Testing may be ineffective (or in some cases, dangerous) for other medications. A history of allergic-type reaction after use of a medication is often considered proof enough of drug allergy -- no further testing is required. The same applies to other substances that are not considered drugs but are used in hospitals, such as x-ray contrast dyes.