What is the time frame in which immediate hypersensitivity reactions (HSR) can occur after the start of an infusion?

Immediate hypersensitivity reactions (HSR), often associated with anaphylaxis, typically occur shortly after exposure to an allergen or infusate. In the context of chemotherapy or immunotherapy infusions, such reactions usually manifest within the first few minutes up to a couple of hours post-infusion initiation.

The identified time frame of within 5 minutes up to 6 hours aligns with the clinical understanding that immediate hypersensitivity reactions can present very quickly, often within just minutes as the immune system responds to substances it identifies as threats. The critical aspect is that these reactions are driven by mechanisms that are activated almost instantaneously — hence the term "immediate" hypersensitivity.

Recognizing this time frame is crucial for healthcare providers, as it enables appropriate monitoring and prompt intervention if an allergic reaction occurs. Understanding that these reactions can occur quickly helps clinicians to remain vigilant during infusion treatments and prepare for potential anaphylactic events, ensuring patient safety.