A patient seated in the chair before a blood draw
In person

Penicillin Allergy Panel (IgE)

IgE to penicillin G and penicillin V, from one blood draw.

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  • 2,000+ lab locations. Find one near you
  • Nothing due at the lab. FSA / HSA accepted
  • Ordered by a licensed clinician

At a glance

Collection
Blood draw
A standard blood draw at the lab.
Preparation
None
Nothing to do ahead of time. Water is fine.
Results
3 to 5 days
Typical turnaround after your visit.
Where
2,000+ lab locations
Nationwide, with nothing due at the lab.

About this test

This panel measures IgE antibodies to penicilloyl G and penicilloyl V, which the lab describes as the major allergenic determinants of penicillin G and V. It is one part of a penicillin allergy evaluation with an allergist, and a negative result alone does not clear the allergy.

For adults 18 and older. Test availability varies by lab location.

Who should take this test?

For adults with a past reaction to penicillin, a rash after an antibiotic, or a penicillin allergy label from childhood, who are working with an allergist on an evaluation.

Ask about this test

Not sure this is the right test?

AI-generated. For information only, not medical advice. Call 911 for an emergency.

What does this test measure?

Your results show whether your blood has IgE to either form of penicillin. An allergist reads them with your history and other tests as one part of a penicillin allergy evaluation.

Penicilloyl G-specific IgE (c1)
Specific IgE is an antibody the immune system can make against one substance. This marker measures IgE that recognizes penicilloyl G, which the lab describes as the major allergenic determinant of penicillin G. A level above the lab’s reference range shows sensitization.
Why it’s measured: Checks for IgE sensitization to penicillin G as one part of a penicillin allergy evaluation.
Penicilloyl V-specific IgE (c2)
Specific IgE is an antibody the immune system can make against one substance. This marker measures IgE that recognizes penicilloyl V, which the lab describes as the major allergenic determinant of penicillin V. A level above the lab’s reference range shows sensitization.
Why it’s measured: Checks for IgE sensitization to penicillin V as one part of a penicillin allergy evaluation.

How it works

  1. Step 1

    Order online

    Check out here. A licensed clinician in your state reviews your order and sends it to the lab.

  2. Step 2

    Visit a lab

    Bring a photo ID to any of 2,000+ lab locations. No fasting needed, and nothing is due at the lab.

  3. Step 3

    Get your results

    Results post to your account, usually in 3 to 5 days, each number next to the lab’s reference range.

Find a lab near you

Choose from 2,000+ lab locations nationwide. Your order works at any of them.

What your results tell you

Each form is reported as an IgE level in kU/L and compared with the lab’s reference range. A level above the range shows sensitization.

  • Your number next to the lab’s reference range
  • Explained in plain language
  • A licensed clinician reviews your order and, if appropriate, orders the test.
  • A lab report you can download and share

Never take a medicine you have reacted to based on this result alone. An allergist reads it with your full history.

Clinical-grade testing, from the comfort of home.

From the lab to your report, every step of our process meets the gold standard in medical testing.

  • CLIA-certified labs

    Every lab we partner with is certified under the Clinical Laboratory Improvement Amendments, meeting both state and federal standards with regular independent inspections.

  • We protect your health data

    We protect your health data with encryption and do not sell it. Some results must be reported to public health authorities by law. See our Privacy Notice.

  • Rigorous quality assurance

    All partner labs run regular internal quality checks, participate in proficiency testing, and comply with federal and state lab regulations.

  • Clinician-reviewed reports

    Results are reviewed by an independent, licensed clinician.

Questions

Common questions.

Anything else, our care team answers by phone, text, or email.

Not on its own. A positive result shows sensitization, which is not the same as an allergy, and a negative result alone does not clear the allergy. This panel is one part of a penicillin allergy evaluation with an allergist.

Never take a medicine you have reacted to based on this result alone. Don’t stop or change any medicine without talking with your healthcare provider.

Get emergency care. If you have trouble breathing, swelling of the face or throat, or you feel faint or pass out after taking a medicine, call 911 right away. If you have a prescribed epinephrine auto-⁠injector, use it as directed. This blood test is not for urgent reactions.

After a serious reaction, an allergist can talk with you about what happened and which tests make sense.

Penicilloyl G and penicilloyl V are forms of penicillin G and V that the lab calls their major allergenic determinants, meaning they are main targets of IgE in penicillin allergy. This panel measures IgE to both.

Amoxicillin, another penicillin-⁠family antibiotic, is tested separately.

Both look for IgE sensitization. A skin test checks how your skin responds to a small amount of an allergen, while this test measures IgE in a blood sample. In many cases the two are considered comparable.

A blood test may be preferred in some situations, such as a widespread skin condition or recent use of medicines that affect skin tests. Don’t stop or change any medicine without talking with your healthcare provider.

Lab tests are informational and don’t diagnose conditions on their own. Available to adults 18 and older; test availability varies by lab location. A licensed clinician reviews your order and, if appropriate, orders the test. All testing is performed at CLIA-certified laboratories. Not for emergencies: if you think you may be having a medical emergency, call 911.