Preoperative Allergies: What You Need to Know Before Surgery

When you’re scheduled for surgery, one of the most critical things your medical team checks is your history of preoperative allergies, allergic reactions that occur before or during surgical procedures, often triggered by medications, latex, or antiseptics. Also known as surgical allergies, these aren’t just about itchy skin—they can cause low blood pressure, breathing trouble, or even cardiac arrest. Many patients assume they’re fine if they’ve never had a reaction before, but allergies can appear suddenly, especially under stress or when combined with anesthesia.

Common triggers include latex, a material used in gloves, catheters, and breathing tubes that causes reactions in up to 8% of healthcare workers and 1-6% of surgical patients, and drugs like neuromuscular blocking agents, anesthesia drugs that paralyze muscles during surgery and are among the top causes of intraoperative allergic reactions. Penicillin and other antibiotics, even if taken years ago, can still cause a reaction when given again. Even iodine-based antiseptics like Betadine can trigger rashes or worse in sensitive people. If you’ve ever broken out in hives after a shot, had trouble breathing after a dental procedure, or had a family member react badly to anesthesia—you need to say it. No detail is too small.

Doctors don’t guess. They ask. And they cross-check your list against what’s in the operating room. A history of egg allergy? That matters if you’re getting propofol. A rash from sulfa drugs? That changes your painkiller options. Even if you think you’re just "a little sensitive," it’s better to over-report than under-report. Many patients skip mentioning seasonal allergies or reactions to shellfish, but those can signal a higher risk for other allergies. Your pre-op checklist isn’t just paperwork—it’s your safety net.

What you’ll find below are real cases, clear explanations of how reactions happen, and what to do if you’ve been told you’re allergic to something that turns out to be a false alarm. Some people think they’re allergic to penicillin because they got a rash as a kid, but 90% of them aren’t truly allergic anymore. Others avoid certain anesthetics because they heard a story, not because they’ve ever had a reaction. We’ll show you how to tell the difference, what tests exist, and how to talk to your anesthesiologist so you’re not left guessing on the day of surgery. This isn’t about fear—it’s about being prepared, informed, and in control of your care.