ADHD: A Parenting Guide

Watch Out For Cross-Reactivity If You Develop An Antibiotic Allergy

If you think you've developed an allergy to a basic antibiotic, talk to an allergy physician as soon as you can. Developing an allergy to a common antibiotic, like penicillin, isn't that uncommon, but there is the chance that you're allergic to more medications. You need to find out which medications or types of medications to avoid and how to handle dealing with infections. Here's a look at why cross-reactivity is an issue and what you can do to stay safe.

Cross-Binding Antibodies

In a true allergy, your body releases antibodies that fight off a supposed invader. The invader can be medication, food, or another external substance--like pollen. There's something about the antigens in the substance in question that your body simply will not tolerate, and your immune system unleashes the antibodies in an attempt to clear your system of the substance.

Sometimes these antibodies react to other substances that are vaguely related to the original allergy's chemical makeup. In the case of penicillin, for example, those antibodies may also react to the antigens in cephalosporins, especially first-generation cephalosporins, even though you might not be allergic to the cephalosporins themselves. With antibiotics, this can be particularly frustrating because the medications are supposed to help you, not make you feel worse!

What You Can Do

Get a list from the allergy doctor of which medications you need to avoid. For penicillin allergies, for example, amoxicillin and ampicillin are commonly off-limits as well. Cephalosporins may be an issue as mentioned; newer-generation cephalosporins might not be as much of an issue as those first-generation medications--but you need to know the risks anyway.

Also try to get an allergy test for other antibiotics if possible. For example, those newer-generation cephalosporins might not be such an issue if all you have is a penicillin allergy. But it's also possible to have a cephalosporin-specific allergy. It's best to see if you can find a group of antibiotics that you can use before you actually get sick. If you aren't sure whether or not you are allergic to a certain group, take note of common antibiotic side effects like:

  • rashes
  • headaches
  • diarrhea
  • candidiasis
  • and abdominal pain

If you have to switch doctors, tell them about the allergies immediately. Don't assume they've read your record. Update any emergency cards you carry to reflect this allergy knowledge. 

If you have questions about antibiotic cross-reactions, contact an allergy physician now. Many times the reactions are mild enough so that they can be stopped before you experience too much discomfort, but reaction intensity can change at any time, and new allergies can form. It's best to be in contact with a doctor who knows how to handle all of these.