Penicillins, including amoxicillin, are among the safest and most effective antibiotics for many infections, and therefore it is important to find out if you are really penicillin (amoxicillin) allergic.
- Penicillins, including amoxicillin, are widely used antibiotics that have important roles in treating bacterial infections.
- Many patients are incorrectly diagnosed with a penicillin (amoxicillin) allergy in childhood, where a viral infection may be the cause of a rash rather than a drug reaction.
- Even in those with true allergy, 50% will lose this tendency in a 5 year period.
- Approximately 10% of the population reports a penicillin (amoxicillin) allergy, but most of these individuals will tolerate penicillin (amoxicillin) after undergoing evaluation.
Penicillin (Amoxicillin) Allergy Diagnosis
Penicillin (amoxicillin) allergy can be evaluated by an allergist/immunologist, who will obtain a careful history and perform allergy procedures, such as skin testing and/or an oral challenge, if indicated. Penicillin (amoxicillin) skin testing is indicated in patients with a reaction history of hives, itching, rash, swelling, shortness of breath, and/or low blood pressure.
Penicillin (Amoxicillin) Skin Testing
- This test involves pricking the skin using a very small plastic device with the forms of penicillin (amoxicillin) that are found in the blood when a patient takes the drug. There are no needles or scratches with this type of allergy skin testing. There is no bleeding or pain with this type of skin testing. The allergist will read the test results 15 minutes after they are placed.
- Development of an itchy, red, raised bump (similar to a mosquito bite) during testing, signifies the presence of an allergy to the medication. If skin testing is positive, a different antibiotic should be used to treat an infection. The itchy, red, raised bump usually completely resolves in an hour.
- If the skin test is negative (no red, raised bump), the allergist will recommend an oral challenge with penicillin (amoxicillin) to be certain that no immediate allergy symptoms develop.
Penicillin (Amoxicillin) Oral Challenge
- If the patient’s skin test is negative, the doctor will recommend an oral challenge in the office. This involves the patient taking increasing doses of liquid penicillin (amoxicillin) every 15 minutes until the full dose is reached.
- If the full dose is tolerated, the patient is not at risk of having a serious immediate reaction and penicillins, including amoxicillin, can be used. It typically takes about 2 hours to perform an oral challenge.
- If a patient is still allergic to penicillin (amoxicillin), they will develop allergy symptoms during an oral challenge. Most times, these symptoms are mild and include mouth itching or a few hives around the mouth. Rarely, a whole body reaction (widespread hives, vomiting, trouble breathing, loss of consciousness) may occur. The risk of this is minimized by starting with a very low oral dose and slowly increasing the dose over time. Additionally, an allergist is prepared to treat a whole body reaction if it occurs.
- If the oral challenge is tolerated without any symptoms developing, the allergist will clear the patient of the penicillin (amoxicillin) allergy and penicillin (amoxicillin) can be used to treat future infections.
Preparing for the Visit
- Penicillin (amoxicillin) testing can be performed at any age, including infancy. This testing should be scheduled at least two weeks after all symptoms that triggered the visit have resolved.
- Penicillin (amoxicillin) testing is scheduled early in the day since it can take up to 2 hours to complete, and in the rare event of a whole body allergic reaction, the patient may need to stay for treatment and observation for several more hours.
- Antihistamines must to be discontinued 5 days before skin testing. These include oral antihistamines such as Benadryl, diphenhydramine, Claritin, loratadine, Zyrtec, cetirizine, Allegra, fexofenadine, Xyzal, levocetirizine, Atarax and hydroxyzine. These also include antihistamine nasal sprays (azelastine, olopatadine) and eye drops (azelastine, Alaway, Zaditor, ketotifen, Pataday, Pazeo and olopatadine).
- H2 blockers (used to treat heartburn/gastroesophageal reflux) must be discontinued 2 days before skin testing. These include Pepcid, famotidine, Tagamet, cimetidine, Zantac, ranitidine, Axid and nizatidine.
- Do not discontinue any asthma medications including montelukast, inhalers or nebulizer medications. There is no need to discontinue nasal steroid sprays such as Beconase, Qnasl, beclomethasone, Zetonna, ciclesonide, Veramyst, Flonase, fluticasone, Nasonex, mometasone, Rhinocort, budesonide, Nasacort and triamcinolone.
- Skin testing and oral challenge testing cannot be performed if a patient is ill (cold, flu, fever, stomach flu, wheezing or uncontrolled asthma symptoms). If these symptoms occur, please call the office to reschedule the visit.