What are the 4 types of allergic reactions?

Type I or anaphylactic reactions which occur in food/drug allergies, hay fever, allergic rhinitis and asthma. Type II or cytotoxic reactions which occur in mismatched blood transfusion, immune mediated hemolysis or thrombocytopenia. Type III or Immunocomplex reactions which occur in Rheumatoid arthritis , Systemic lupus Erythematosus. Type IV or cell mediated reactions is a delayed hypersensitivity which occur few hours after exposure to any allergens.