This is a prospective, randomized, double-blind controlled trial to evaluate the efficacy of placebo versus chlorpheniramine for the prevention of allergic transfusion reactions.

Inclusion Criteria:

• 18~65 years old.
• Subject is diagnosed with hematological disorder and requires blood product (i.e. suspended red blood cells, apheresis platelets, fresh frozen plasma) transfusions.
• Subject can fully understand and voluntarily sign informed consent forms.

Exclusion Criteria:

• Subject with a history of allergic diseases.
• Subject experienced at least 1 moderate/severe or 2 mild allergic reactions in the past.
• Subject received glucocorticoid or allergy drugs within 24 hours before blood transfusion.
• Subject transfused with washed RBC.
• Received allo-HSCT transplantation before.
• Subject with heart failure.
• Subject suffered from sequelae of cardiovascular or cerebrovascular diseases.
• Pregnant or nursing women.
• Inability to understand or to follow study procedures.

Neither patients nor medical staff, including physicians and nurses participating in this study, will know the group assignment after allocation.