How long before undergoing allergy testing should I cease the intake of antihistamines? Is there a universally accepted timeframe, or does it vary based on the specific medication and its half-life? Furthermore, could the timing be influenced by individual factors such as metabolism, age, or severity of allergic symptoms? For instance, if one has been utilizing a non-sedating antihistamine, would the required cessation period differ markedly from that of a first-generation antihistamine, which might linger longer in the system? Additionally, what are the potential implications for the accuracy of test results if one were to stop the medication too soon or even too late? Should I anticipate experiencing a resurgence of allergic symptoms during this waiting period, and how might that influence my decision on when to discontinue usage? Ultimately, what evidence-based guidelines exist to inform patients about the optimal time frame for halting these medications prior to testing?