By Gary M. White, MD

Serum sickness-like reaction

Serum sickness-like reaction (SSLR) is a drug reaction characterized by rash (urticarial or morbilliform), fever, and arthralgias without evidence of cutaneous or systemic vasculitis. Unlike serum sickness reaction, a type III hypersensitivity reaction with immune complex deposition, the pathophysiology of SSLR is not thought to be immune complex mediated [JAAD;2011;65;e83–e85].

SSLR is a characteristic syndrome usually in response to an antibiotic. The most classic being cefaclor but also other cephalosporins, penicillins, tetracyclines, sulfonamides and occasionally other classes of medications.


The child develops red, inflammatory nodules that spread out to form annular plaques, often with dusky centers. The term "purple urticaria" has been used. Onset is usually 1-2 weeks after the patient begins the medication. Fever and joint pains are typical. Lymphadenopathy may occur. In contrast to true serum sickness-like reaction, kidney damage is not seen.

Differential Diagnosis

See here.


Any medications suspected as the cause should be stopped. If needed prednisone 1-2 mg/kg/day can cause dramatic improvement.

Additional Photos

The same child early (comparison with above shows the progression of the lesions).
Serum sickness-like reaction Serum sickness-like reaction Serum sickness-like reaction Serum sickness-like reaction Serum sickness-like reaction


Home | FAQs | Use of Images | Privacy Policy | Contact

It is not the intention of to provide specific medical advice, diagnosis or treatment. only intends to provide users with information regarding various medical conditions for educational purposes and will not provide specific medical advice. Information on is not intended as a substitute for seeking medical treatment and you should always seek the advice of a qualified healthcare provider for diagnosis and for answers to your individual questions. Information contained on should never cause you to disregard professional medical advice or delay seeking treatment. If you live in the United States and believe you are having a medical emergency call 911 immediately.