Think You Have A Penicillin Allergy The Good News Is You May Not
Roughly 10% of the population believes they have a penicillin allergy. The truth is that fewer than 10% of people with a reported penicillin allergy actually have one. This topic has garnered significant attention recently after a large review article published by the Journal of the American Medical Association highlighted this important issue. The article jointly endorsed by the American Academy of Allergy, Asthma and Immunology, the Infectious Diseases Society of America, and the Society for Healthcare Epidemiology of America urges individuals who have been diagnosed to confirm with a certified allergist for a variety of reasons.
Even if someone had a true allergic reaction to penicillin, this particular allergy often dissipates after about ten years. Once someone has confirmed with an allergist that they are no longer allergic, the patient often times has better future treatment of infections, fewer dangerous side effects of the antibiotics used in place of penicillin, and overall lower cost of care. Penicillins tend to be safer to use than the antibiotics which are used instead in those who are labeled as allergic.
Our 3 board-certified allergists are happy to help confirm if you have a penicillin allergy. You can schedule an appointment by calling us at 641-6134.
So, what do you need to know about Penicillin?
1. What is penicillin?
2. How common in penicillin allergy?
3. How do I know if I am still allergic to penicillin?
4. Is penicillin allergy genetic?
How Common Is Penicillin Allergy
According to the Centers for Disease Control and Prevention, less than 1 percent of people have a true penicillin allergy, even though about 10 percent of people tell their doctors they are allergic to penicillin.
Sometimes, a common reaction to penicillin is mistaken for an allergy. In other cases, a person may report a family history of penicillin allergy, but penicillin allergy is not passed down through families.
Other Beta Lactam Antibiotics
Penicillins are beta lactam drugs but in case of allergy to penicillins, other beta lactam drugs can be used safely. Besides penicillins, other beta lactams are given as such:
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Antibiotic Choice For Children With Penicillin Allergy
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It is not uncommon for caregivers or older pediatric patients to inform their pediatric health care provider of an allergy to penicillin. The lay public often loosely uses the word allergy with regard to medications, but hearing penicillin allergy by a health care provider is likely to raise a red flag. Eliminating the use of penicillin, amoxicillin and other beta-lactam antibiotics because of an allergy presents significant implications for antibiotic choice and infectious disease treatment.
Types of reaction
As readers of this column are aware, perhaps the most useful question to ask a caregiver or patient about a penicillin allergy is the type of reaction the patient experienced. A history of nausea, vomiting, loose stools or diarrhea when the antibiotic was taken may have been distressing to the caregiver or patient, but these effects are certainly not indicative of a type I allergic reaction the allergic reaction that is most concerning to health care providers.
Edward A. Bell
Cephalosporins as an alternative
Likely not a true allergy
References:
Campagna JD. J Emerg Med. 2012;42:612-620.
For more information:
Disclosure: Bell reports no relevant financial disclosures.
Are Keflex And Penicillin Safe To Use While Pregnant Or Breastfeeding

Keflex
Cephalexin is excreted in breast milk. Cephalexin should be used with caution or stopped when breastfeeding.
Penicillin
Penicillin antibiotics are considered safe to use during pregnancy. Although small amounts of penicillins pass into breast milk they are considered safe to use while breastfeeding.
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What Antibiotic Can You Take If You Are Allergic To Penicillin
Kids or adults who are allergic to penicillin may be able to take one of these antibiotics instead:
- Azithromycin
- Cephalosporins, including cefixime , cefuroxime , and cephalexin
- Clarithromycin
It is generally recommended that you avoid all drugs in the immediate penicillin family .
Beside above, what antibiotics can you take if you are allergic to amoxicillin? Amoxicillin belongs to a group of antibiotics called Penicillins. If you are allergic to Penicillins then you are more likely to be allergic to a group of antibiotics called Cephalosporins of which Cephalexin is a member. Cephalexin should be avoided in a penicillin allergic patient.
Then, can you take amoxicillin if you are allergic to penicillin?
No, you should not take amoxicillin if you are allergic to penicillin. Amoxicillin belongs to the Penicillin class of antibiotics and must be avoided. You need to see your dentist and/or doctor with an infected tooth.
Can you take Keflex if allergic to penicillin?
Cephalosporins can be prescribed safely for penicillin–allergic patients. The widely quoted cross-allergy risk of 10% between penicillin and cephalosporins is a myth. Cephalothin, cephalexin, cefadroxil, and cefazolin confer an increased risk of allergic reaction among patients with penicillin allergy.
What Drugs Interact With Keflex And Penicillin
Keflex
Cephalexin may reduce the effect of BCG and typhoid vaccines. Cephalexin should not be combined with BCG or typhoid vaccine unless there are no other options.
Penicillin
Penicillin antibiotics have few important drug interactions.
- Probenecid causes an increase in the amount of penicillins in the body by preventing excretion of penicillin by the kidneys.
- Combining ampicillin with allopurinol can increase the incidence of drug-related skin rash.
- Penicillin antibiotics may reduce the effect of BCG live vaccine and typhoid live vaccine.
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When Should I Get Tested
I am often asked to evaluate penicillin allergies when a patient needs penicillin or another beta-lactam, and the documented allergy is obstructing the best treatment. However, the best time to have a penicillin allergy evaluated is when youre healthy.
You can discuss allergies as part of routine health maintenance with a primary care doctor or pediatrician. Clarifying medication allergies is also a good idea before an operation; a penicillin allergy can impact infection risk, and allergies to latex and pain medications can get in the way of a smooth operation and post-operative period. Finally, women of childbearing age who are thinking of conceiving might want to evaluate an allergy to penicillin. Penicillins are used for infections in pregnancy and during deliveries for a variety of reasons. Pregnant patients can also be evaluated safely for a penicillin allergy in their third trimester.
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Drug Therapy And Emergency Medical Care
A mild allergic reaction can be treated with an antihistaminics like diphenhydramine, which helps relieve itching and skin rash. However, serious anaphylactic reactions require the urgent administration of adrenalin to counter the cardiac collapse as well as corticosteroids to counteract the effect of the mediators released from the mast cell. In the case of a true anaphylactic hypersensitivity reaction, a patient may die unless controlled with adrenaline and their airway is maintained.
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Is Amoxicillin Or Penicillin Better
Amoxicillin or penicillin may be more effective depending on the bacterial infection being treated. Amoxicillin can cover infections caused by other types of bacteria such as E. coli, Salmonella, and H. influenzae. Penicillin may be better to target specific types of bacteria in order to prevent antibiotic resistance.
Managing Persons Being Tested
Patients who have a positive skin test should not receive ß-lactam drugs in the ambulatory setting and should be referred to an allergist or penicillin allergy expert for further evaluation. The allergy testing results should be documented in the medical record. Patients who test negative should be informed that their risk for anaphylaxis is extremely low and is equivalent to a person who does not report an allergy history. If treatment with penicillin or ceftriaxone is indicated, it can be administered safely. Documentation of testing results should be provided to the patient.
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Warnings Of Amoxicillin And Penicillin
Serious hypersensitivity and allergic reactions have been reported with amoxicillin and penicillin. Allergic reactions may lead to anaphylaxis or anaphylactic shock. If you experience difficulty breathing, severe rash, and severe nausea, seek medical attention immediately.
If you are prescribed a course of amoxicillin or penicillin treatment, its important to finish all of the antibiotics even if youre feeling better. If you dont finish treatment, the bacteria may have a chance to mutate and develop resistance to the antibiotic. This can lead to a more severe infection that would require further treatment.
Talk to your doctor if you experience or have a history of the following:
- Diarrhea after taking antibiotics
Penicillin Amoxicillin And Cephalosporin Allergy: What To Know

Penicillin is perhaps the most well-known member of a group of antibiotics called beta-lactams, which refers to a particular structure in their chemical makeup. The structure is also shared by semi-synthetic penicillin , cephalosporins, and other antibiotics, such as imipenem. Penicillins and cephalosporins are the antibiotics most commonly used to treat common bacterial infections.
Unfortunately, penicillins and cephalosporins are also the most common causes of drug allergy. About 10% of Americans report having an allergy to penicillin or a related antibiotic. In fact, however, the number of people who have a true penicillin allergy is much lower.
While penicillin allergy most frequently occurs in young adults, reactions can occur at any age. Women appear to be at higher risk than men. Reactions to penicillin may include anaphylaxis, hives, below-the-skin swelling, and asthma symptoms, as well as non-allergic symptoms such as serum sickness, certain forms of anemia, and other drug rashes.
The family of penicillin antibiotics includes:
- Penicillin VK
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Patients At Low Risk For Oral Challenge
If the patient gives only a low-risk history of IgE-mediated penicillin allergy that includes symptoms such gastrointestinal intolerance, headache, fatigue, or nonspecific pruritus, or gives a family history only, an oral challenge can be administered to document the absence of allergy . If the reaction occurred in the distant past , the likelihood is reduced even further . The risk for severe amoxicillin-mediated anaphylaxis has decreased over time and is rare. In the United Kingdom during 19722007, one fatal case of amoxicillin-medicated anaphylaxis was reported .
Is Amoxicillin Or Penicillin More Effective
Although both antibiotics are effective for treating bacterial infections, their effectiveness depends on the bacteria causing the infection. Amoxicillin is able to get rid of a broader range of bacteria compared to penicillin. Although both antibiotics are effective against streptococci, amoxicillin is more effective against E. coli and H. influenzae, among others.
According to a 2018 systematic review, amoxicillin is better for treating community-acquired pneumonia compared to penicillin. However, results showed that penicillin may be better for respiratory tract infections in general due to its narrow coverage. There was no significant difference between the two antibiotics when treating otitis media.
One of the primary goals of fighting bacterial infections is to prevent resistance. Bacterial resistance can lead to stronger infections which can be harder to treat. This is why knowing what bacteria is causing the infection is important. Talk with your healthcare provider to find the best treatment option that works for you.
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What Is Penicillin Used For
Penicillin works on many types of bacterial infection, unless the infection is resistant to it.
Your doctor might prescribe you a type of penicillin if you have a:
- skin infection
Less common side effects include:
- shortness of breath or irregular breathing
- abdominal cramps, spasms, tenderness or pain
- vaginal itching and discharge, due to either a yeast infection or bacterial vaginosis
Serious side effects of penicillin are rare and include:
- difficulty breathing due to a severe allergic reaction
- sudden and
Conditions Treated By Amoxicillin And Penicillin
Amoxicillin and penicillin can treat many different bacterial infections including lower respiratory tract infections and dental infections. Amoxicillin and penicillin are commonly prescribed to treat middle ear infections, otherwise known as otitis media. Both antibiotics can also treat certain infections of the urinary tract and skin.
Amoxicillin is FDA-approved to treat bacterial infections such as gonorrhea. It can also treat H. pylori infections and throat infections like pharyngitis and tonsillitis. For respiratory tract infections like community-acquired pneumonia , amoxicillin is an option in areas with low antibiotic resistance.
Penicillin is often used to treat bacterial endocarditis, scarlet fever, and dental infections. Skin infections caused by Staphylococcus aureus can also be treated with penicillin, although the penicillin G form is preferred.
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Bulwark Against Bigger Problems
The risk of administering penicillin to a patient who is allergic to it is real, Kalra acknowledged, but greatly outweighed by the dangers of giving an antibiotic that is more powerful than needed, like clindamycin. In addition to increasing the risk of serious infection, such broad spectrum antibiotics, if not properly targeted, can unleash wide-ranging attacks on the guts flora, lengthening hospital stays, contributing to the growing threat of antibiotic resistance and sometimes leading to death.
Its a huge problem, Kalra said. Penicillin is a very important class of antibiotic, and the ability of our patients to take them is very important.
The Pre-Procedure Services and Allergy and Asthma clinics cant yet test all patients with a penicillin allergy listed, Selzer said. But she noted that all patients who have been referred for testing thus far have had negative results and had their penicillin allergies removed from the medical records.
General Approach To Beta
For most patients presenting to critical care with an acute infection, logistics don’t allow for sophisticated approaches such as skin testing or desensitization.; Fortunately, we can generally select safe and effective antibiotics simply based on understanding which antibiotics are truly cross-allergic with each other.
As discussed above, the degree of cross-reaction is far lower than has previously been believed.; For example, there’s no such thing as a penicillin allergy to all penicillins.; By breaking down cross-allergic medications into smaller groups, we can generally manage to find an adequate antibiotic which is not cross-allergic with medications that the patient is allergic to.
Overall, the incidence of anaphylaxis due to cephalosporins is about ten times lower than for penicillins.; This may reflect that the molecular structure of cephalosporins is less likely to break apart and stick to proteins .; However, different medications vary considerably in their likelihood of eliciting allergic reactions.
It’s important to realize that the risk of an anaphylactic reaction is never zero, for any patient or with any medication.; Patients with a history of anaphylaxis to one medication may be more likely to develop anaphylaxis to other medications in general.; As is often the case in medicine, our task is to minimize risk as much as possible but we can never get to zero risk.; In fact, attempting to achieve zero risk could merely lead to more harms .
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How Is Penicillin Allergy Treated
Other than the immediate treatment of drug allergy symptoms, the main treatment for penicillin allergy is avoidance of future use of penicillin and related antibiotics. However, if penicillin is required, people with penicillin allergy can also be admitted to a hospital for a desensitization procedure.
Coverage And Cost Comparison Of Amoxicillin Vs Penicillin

Amoxicillin is a commonly prescribed antibiotic that is almost always covered by Medicare and insurance plans. The typical average cost of amoxicillin is around $24. However, a SingleCare discount card can lower this cost to around $5. Amoxicillin is usually purchased as a generic tablet, capsule, or oral liquid.
Like amoxicillin, penicillin is also widely available and covered by most insurance plans. If you are picking up penicillin from the pharmacy, it will most likely be the penicillin V or penicillin VK form. The average cost of penicillin V is $40. However, with a SingleCare discount card, this cost can be lowered to around $9. The cost will depend on which pharmacy you use and whether you get the pill or liquid form.
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Diagnosis Of Antibiotic Allergy
The patient history is often the only tool available for making the diagnosis of antibiotic allergy. The main goal is to establish whether the patient had an IgE-mediated reaction to an antibiotic, which could manifest as urticaria, pruritus, angioedema, hyperperistalsis, bronchospasm, hypotension, and/or arrhythmia.
Patients generally develop allergic reactions when reexposed to an antibiotic or during the second week of a course of treatment with an antibiotic they have never received in the past. It is unusual for a patient to have an allergic reaction to an antibiotic they have been receiving continuously for months. Atopic individuals do not have a higher incidence of penicillin allergy, but they possibly have a higher risk of experiencing severe penicillin allergy .
Parents are often concerned that antibiotic allergy will be inherited. A study showed a high incidence of reported antibiotic allergies in children whose parents had a history of antibiotic allergy , but no attempt was made to verify these allergies. Often children appear to be allergic to different drugs than are their parents .
The presence of eosinophilia may support a diagnosis of drug allergy if there are compatible signs and symptoms, but the positive predictive value of eosinophilia is unknown. Treatment with an antibiotic does not need to be withdrawn if it is causing eosinophilia but the patient shows no other evidence of hypersensitivity .