Side Effects of Amoxicillin

By Katharine Paljug  @YourCareE
February 17, 2023
Side Effects of Amoxicillin

Many children are susceptible to the uncommon side effects of amoxicillin, used to treat bacterial infections, but they may outgrow their allergies as adults.

Amoxicillin is an antibiotic in the same family as penicillin, one of the most common drugs that doctors prescribe. Amoxicillin is used to treat bacterial infections. The medicine attacks disease-causing bacteria, killing them and preventing them from spreading throughout your body.

Like penicillin, amoxicillin is less expensive for patients than many other antibiotics, and it usually causes few side effects. This makes it a popular choice for doctors to prescribe for mild bacterial infections, including infections of the skin, throat, ear, sinuses, and upper respiratory tract. It can also be used in combination with other drugs to treat stomach ulcers.

Because of its lack of side effects when compared to other antibiotics, amoxicillin is frequently prescribed for children. There are side effects of amoxicillin, however. If your child has an allergy to amoxicillin, using it to treat an infection can cause more harm than good.


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Children’s allergies to amoxicillin

Most amoxicillin allergy symptoms appear in similar ways.

One study of amoxicillin allergies reported that the most common side effect of amoxicillin is the appearance of hives or a red skin rash. Though uncomfortable, this reaction is usually mild and will resolve on its own. More severe allergic reactions are rare, but they can include anaphylaxis, fever, flu-like symptoms, skin pustules, and blistering.

Many times, children will react to the antibiotic quickly, often less than an hour after taking a dose. This is classified as an immediate reaction. Some children, however, take longer to react; these non-immediate reactions take more than an hour and may not appear for up to five days.

Studies have found that non-immediate reactions can make diagnosing allergies to amoxicillin difficult for pediatricians, especially since the timing of a reaction does not necessarily correspond with how severe it is.

Side effects of amoxicillin in children are usually discovered only after a child has been prescribed the antibiotic to treat an infection. Children with known allergies to penicillin, however, should generally be tested for allergies to amoxicillin as well.

A report in the journal of Allergy, Asthma, and Immunology Research recommends checking for side effects of amoxicillin with a patch test on the skin to see if any reaction occurs. A patch test generally causes a mild skin reaction, rather than more severe symptoms, and can indicate whether further testing is necessary.

Amoxicillin allergies in adults

Amoxicillin allergies in adults present with similar symptoms to those in children. They are much less common, however.

According to a report by NBC News, many adults who believe they are allergic to antibiotics in the penicillin family are mistaken. That’s because over 50 percent of adults will outgrow a childhood penicillin allergy, including allergies to amoxicillin. In one study, half of adults who thought they had allergies really didn't.  

In some adults, the allergy may have been misdiagnosed or was likely due to an additive that was mixed with the amoxicillin they received as a child, rather than the antibiotic itself. Some studies have found that amoxicillin allergies are often not “true” allergies, meaning they are not a reaction in the immune system, making them more likely to disappear after childhood.

As a result, adults who think they suffer side effects of amoxicillin should be retested to see if they still react. Methods can include a patch test or a drug challenge test, when the antibiotic is administered orally and a doctor monitors your reaction to see if you still show signs of an allergy.

Being able to take amoxicillin, rather than more expensive antibiotics, will save you money when you have a bacterial infection, but that’s not the only benefit to checking whether you are still allergic. When doctors can prescribe amoxicillin, they can save stronger antibiotics to treat more severe infections or dangerous bacterial strains which are penicillin-resistant.


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February 17, 2023

Reviewed By:  

Janet O’Dell, RN