CME information and disclosures
To see contributor disclosures related to this article, hover over this reference: 
Physicians may earn CME/MOC credit by reading information in this article to address a clinical question, and then completing a brief evaluation, in which they will identify their question and report the impact of any information learned on their clinical practice.
AMBOSS designates this Internet point-of-care activity for a maximum of 0.5 AMA PRA Category 1 Credit(s)™. Physicians should claim only credit commensurate with the extent of their participation in the activity.
For answers to questions about AMBOSS CME, including how to redeem CME/MOC credit, see “Tips and Links” at the bottom of this article.
Serum sickness is a type III hypersensitivity reaction that usually develops as a complication of antitoxin or antivenom administration, but can also occur after antibiotic administration and hepatitis B infection. Symptoms typically occur 1–3 weeks after exposure to the offending agent and include fever, rash, and arthralgia. It is diagnosed clinically and treatment consists primarily of removing the offending agent.
- Antivenom or antitoxin containing animal proteins or serum (→ “serum” sickness), such as:
- Medications: most frequently antibiotics (e.g., penicillin, amoxicillin, cefaclor, trimethoprim-sulfamethoxazole) 
- Infections: Hepatitis B virus
- Rash (urticarial or purpuric)
- Arthralgias, myalgia
- Hand edema
- Headache, blurred vision
- Abdominal pain, diarrhea, nausea/vomiting
- Mucosal involvement is uncommon
Symptoms appear 1–3 weeks following initial exposure (because antibodies take several days to form) and typically resolve within a few weeks after discontinuation of the offending agent.
See also “Hypersensitivity reactions.”
Serum sickness-like reaction
- Epidemiology: much more common than actual serum sickness
- Etiology: similar to that of serum sickness
- Pathogenesis: unclear (likely not the result of a type III hypersensitivity reaction)
- Clinical features
The differential diagnoses listed here are not exhaustive.