• hives (common)
• skin rash (common)
• itching of the skin or eyes (common)
• wheezing
• swelling of the lips, tongue, and/or face
• anaphylaxis, or severe allergic reaction (see below)

• difficulty breathing with wheeze or hoarse voice
• hives over different parts of the body
• fainting, light-headedness
• dizziness
• confusion
• rapid pulse
• sensation of feeling the heart beat (palpitations)
• nausea, vomiting
• diarrhea
• abdominal pain or cramping

An examination of the skin and face may show hives, rash, or angioedema (swelling of the lips, face, and/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 adequately diagnostic for drug allergy. (No further testing is required to demonstrate the allergy.) The same applies to other substances that are not considered drugs but are used in hospitals, such as X-ray contrast dyes.