Serum is the fluid left over when blood cells are taken out of the blood. Serum sickness refers to a set of symptoms that occurs when a person's immune system reacts to a medication or other similar substance. It is a type of allergic reaction.
A person with serum sickness has an immune system reaction after taking a medication or similar substance. The immune system makes proteins called antibodies to attack the medication. This reaction of the immune system causes inflammation throughout the body and the symptoms of serum sickness. In most cases, when the person stops using the medication or other substance, the symptoms go away.
Serum sickness is most often caused when a person takes or receives one of the following substances:
Other substances may also cause this condition.