<unk>  is a reaction similar to an allergy. Specifically, it is an immune system reaction to certain medications, injected proteins used to treat immune conditions, or antiserum, the liquid part of blood that contains antibodies that help protect against infectious or poisonous substances.
Serum sickness
Adult-onset Still's disease
Relapsing fever
COVID-19 Nephrologic Complications
Periodic fever syndrome
Arthritis-dermatitis syndrome
DRESS syndrome
Rabies