Why is it important to know a patient's allergies before administering medication?

Understanding a patient's allergies before administering medication is crucial because it directly relates to patient safety. Allergic reactions can lead to severe, sometimes life-threatening conditions such as anaphylaxis, which can occur quickly after medication administration. By being aware of a patient's allergies, healthcare providers can avoid prescribing or giving medications that could trigger such reactions, thus ensuring the patient's well-being.

In contrast, while factors like affordability and adherence to hospital policy are important in a healthcare setting, they do not directly impact the immediate safety of the patient regarding medication administration. Additionally, medication effectiveness is relevant but secondary to the immediate need to ensure that the patient will not have an adverse reaction to the medication. Therefore, the priority must always be the avoidance of potential allergic reactions when considering any treatment.