S.No

Type of Agent

Name of the Agents

Defect

Mechanism

I.

Physical Agents

1. Irradiation

2. Light and Cold

Antigenic alteration

Photosensitivity and Cold energy

Sensitization

Sensitization to self

II.

Chemical Agents

1. Chemical Allergens

2. Drugs

Contact Dermatitis

Anemia, Leucopenia, Thrombocytopenia

Skin antigens altered by their combination with chemical allergens.

Autoimmunity

III.

Biological Agents

1. Virus

2. Neuraminidase-enzyme produced by many bacteria and Myxoviruses

Infectious mononucleosis

Autoimmune response

Autoimmunity

Act on erythrocytes releasing the T-antigen.