<unk>  is a type III hypersensitivity reaction, caused by immune complexes. When an antiserum is given, the human immune system can mistake the proteins present for harmful antigens. The body produces antibodies, which combine with these proteins to form immune complexes. These complexes precipitate, enter the walls of blood vessels, and activate the complement cascade, initiating an inflammatory response and consuming much of the available complement component 3 (C3). They can be found circulating in the blood, which differentiates<unk>  from<unk> -like reaction. The result is a leukocytoclastic vasculitis. This results in hypocomplementemia, a low C3 level in<unk> . They can also cause more reactions, causing the typical symptoms of<unk> . This is similar to a generalised Arthus reaction. Antitoxins and antisera<unk>  is usually a result of exposure to antibodies derived from animals. These sera or antitoxins are generally given to prevent or treat an infection or envenomation (venomous bite). Drugs<unk>  may be caused by some routine medications. Some of the drugs associated with<unk>  are: * allopurinol. * barbiturates. * captopril. * cephalosporins. * crofab. * griseofulvin. * penicillins. * phenytoin. * procainamide. * quinidine. * streptokinase. * sulfonamides. * rituximab. * ibuprofen. * infliximab. * oxycodone. Others Allergenic extracts, hormones and vaccines can also cause<unk> . However, according to the Johns Hopkins Bloomberg School of Public Health, routinely recommended vaccinations to the general population in the U.S have not been shown to cause<unk> , as of 2012.
Serum sickness
Erythema multiforme
Disseminated disease
Hives
Adult-onset Still's disease
Lupus
Relapsing fever
SAHA syndrome