What's the "een" in Halloween?
serum sickness n.
A hypersensitive reaction to the administration of a foreign serum, marked by fever, swelling, skin rash, and lymph node enlargement. Also called serum disease, serum reaction.
an allergic reaction to animal serum or antiserum injected into an individual's blood to provide immunity against such illnesses as tetanus, botulism, and snake-venom poisoning. Symptoms include skin eruption, itching, swelling of the face and extremities, fever, joint pain and sometimes swelling, abdominal pain, nausea, and vomiting; severe cases may also show neurological symptoms.