Serum sickness is an allergic reaction to an antiserum that is injected into your body to help fight an infection or antitoxin that is administered after exposure to a toxin.
Antiserum and antitoxin are animal or human proteins that are foreign to your body and therefore may result in an allergic reaction if your body mistakes them for an infectious agent.
Symptoms of Serum Sickness
Symptoms appear after about 14 days, but subside within 5 days if you cease taking the antiserum.
Treatment of Serum Sickness
Corticosteroids or antihistamines may be administered to relieve symptoms, but the best thing to do is discontinue taking the antiserum that caused the reaction.