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Drug Info

How to identify and treat an amoxicillin rash

This common antibiotic can cause skin reactions, but that doesn’t necessarily indicate an allergy
Ben Michalak
By | Nov. 6, 2023 Medically reviewed by Laura K. Grubb, MD, MPH
Two arms itching — amoxicillin rash

Key takeaways

  • Amoxicillin is a commonly used antibiotic that can cause rashes in some patients, which does not always indicate an allergy.

  • There are two main types of amoxicillin rashes: non-allergic rashes, which appear a few days after starting the medication, and allergic reactions, which occur within hours and require immediate medical attention.

  • Treatment for an amoxicillin rash may include stopping the medication, taking antihistamines for symptom relief, and an epinephrine injection or drug desensitization for allergic reactions.

  • Causes of an amoxicillin rash can include the body’s immune response, a history of allergic reactions to antibiotics, destruction of the gut microbiome, sensitization from other infections, or drug interactions.

In this article:

Amoxicillin is one of the most commonly used antibiotics for treating bacterial infections. Known for its ability to stop the growth of bacteria, amoxicillin is also one of the most tolerable drugs for children and is prescribed by pediatric healthcare providers over others in the penicillin family, such as ampicillin or oxacillin. 

As a parent or patient, you may be concerned about reactions to a new medication, especially if they point toward an unknown drug allergy. Amoxicillin is known for causing rashes in certain patients, but the good news is that most don’t indicate an allergy. Many people assume if they get a rash after taking amoxicillin that they are allergic to penicillin. In reality, while 10% of the population reports a penicillin allergy only 1% of people are truly allergic to it.

There is a slim chance that a rash could indicate a true allergic reaction to amoxicillin, so it’s important to know how to identify the type of rash and what to do for each kind. Here’s what to do if you or your child experiences a skin reaction after starting this popular antibiotic.

Can you get a rash from amoxicillin?

Yes, you can get a rash from amoxicillin. There are two types of amoxicillin rashes: non-allergic and allergic reactions.

Non-allergic rashes typically appear three to seven days after starting amoxicillin but may occur at any time throughout the course of treatment. Although it may seem concerning, children who experience these rashes don’t report itching or hives. Many times, people who have viral infections will have a viral rash and the timing with amoxicillin is coincidental. For example, for persons with Epstein Barr virus (mononucleosis), amoxicillin exposure produces a sensitivity response that is a rash.

Allergic reactions start within hours of taking the first dose of amoxicillin. Contact a healthcare provider immediately for instructions on what to do next. Allergic reactions are serious and require immediate attention.

In most cases, amoxicillin rashes are a side effect of the medication (especially for mononucleosis) and not allergic reactions. About 5%-10% of children develop a rash from amoxicillin, but only a small number of those are due to allergic reactions. 

How long does an amoxicillin rash last?

Non-allergenic amoxicillin rashes last one to six days, with most going away after just three. But allergic rashes can take a few weeks to clear up completely.

Do not stop taking amoxicillin unless directed to do so by a healthcare professional. Just because you stop taking amoxicillin doesn’t mean the rash will go away faster—and you run the risk of the original infection coming back and making you feel worse. 

What does an amoxicillin rash look like?

Amoxicillin rashes vary in appearance. Some patients experience flat, red patches, while others encounter raised hives, says Kelvin Fernandez, MD, a resident physician at Newark Beth Israel Medical Center in New Jersey. “The key to identifying an amoxicillin rash lies in its timing,” he says. 

Common, non-allergic rashes often manifest as tiny pink or red bumps called a maculopapular rash, or a delayed skin rash, given that it takes a few days to appear. You’ll see it on the chest, around the abdomen, and back, but it may also spread to the face, arms, and legs. Although it’s not a usual sign of an allergic reaction, it should be reported to a healthcare provider if you experience difficulty breathing. 

Allergic rashes will appear within an hour of starting a medication. Hives, which are a warning sign of an allergic reaction, look like raised welts that change location and cause significant itchiness. Unlike maculopapular rashes, hives are blotchy, swollen, and move around the body. Though hives are commonly a reddish pink, they will also blanch, meaning it will turn white after pressing down on it. Hives often resemble mosquito bites. In addition to hives, you may experience facial swelling, wheezing, shortness of breath, anaphylaxis and trouble swallowing. If this happens, see a healthcare provider immediately. 

Maculopapular rashes and hives are different types of rashes. Rashes are more the sign of irritation, whereas hives point toward a possible amoxicillin allergy. Hives are raised, and rashes are flush. Most hives are sealed and do not break open, while with rashes, you may experience blistering. 

How to treat an amoxicillin rash

There are a few ways to treat an amoxicillin rash. It involves first, treating the current rash symptoms and then treating the allergy (for allergic rashes).

To treat non-allergic or allergic rash symptoms, your healthcare provider may suggest stopping the amoxicillin and prescribe an additional medication, such as over-the-counter antihistamines such as Benadryl (diphenhydramine) can help reduce rashes and relieve itching. You can also try home remedies including:

  • Keeping skin moist
  • Taking oatmeal (colloidal) baths
  • Applying cool compresses

Most amoxicillin rashes are not allergic reactions and will go away in a matter of days. Maculopapular rashes are not contagious and typically do not irritate the skin.

For allergic rashes, if you experience anaphylaxis with hives, you will need an epinephrine injection. Depending on the severity of your reaction, you may require blood pressure and breathing support. If you have an allergic reaction (hives and anaphylaxis) within hours of your first dose, contact a healthcare provider or seek emergency medical attention immediately.

The only cure for a rash from penicillin allergy is drug desensitization where you receive a small dose of amoxicillin every 15 to 30 minutes over a few hours or days under a provider’s supervision. Then, if you reach the prescribed doses without a reaction you can take the medication. This is usually a method only used when amoxicillin is the only therapeutic medication available for an infection. 

What causes an amoxicillin rash?

There are several causes of amoxicillin rashes:

  • An immune system reaction: Amoxicillin disrupts your body’s immune system by blocking bacteria’s ability to make and repair protective cell walls. “Infants and small children are at a greater risk of developing an amoxicillin rash because their immune systems are not yet fully developed,” says Krista Elkins, RN, an emergency nurse and paramedic based in Bozeman, Montana. If your child experiences a rash after taking amoxicillin, chances are it’s a mixture of their body reacting to the amoxicillin and the virus itself. This isn’t an indication of a penicillin allergy. 
  • History of allergic reaction to antibiotics: Drug hypersensitivity reactions can be frightening, but you can preempt them by visiting an allergist. They can conduct skin tests, determine your or your child’s potential allergies to medications, and give medical advice about how to avoid allergens in the future. 
  • Destruction of the gut microbiome: “While the exact mechanism is unknown, it is believed that a virus causes the rash because the antibiotics have destroyed all the natural gut microbiome, which is responsible for a healthy immune system,” Elkins says. 
  • Sensitization from other infections: Sensitization, when the immune system reacts to a substance by deploying antibodies, is a possible cause of a rash. A history of mononucleosis, or mono, has been known to be a factor that increases the risk of rash with amoxicillin. 
  • Drug interactions: Other medications you are taking can also cause adverse reactions. In addition to allopurinol and other uric acid reducers, tell your healthcare provider if you’re taking birth control pills or blood thinners if you are prescribed amoxicillin for a bacterial infection.

What can I take instead of amoxicillin?

An amoxicillin allergy can be limiting in terms of what other drugs in the penicillin family you can take. For example, ampicillin and augmentin are two drugs similar to amoxicillin and should be avoided if you have a true allergy. However, there are a few amoxicillin alternatives a healthcare provider may prescribe, including: 

  • Cephalexin
  • Cefdinir
  • Azithromycin (Generally contraindicated in children younger than 8 years old due to dental staining unless there are no other therapeutic options.)
  • Doxycycline (Generally contraindicated in children younger than 8 years old due to dental staining unless there are no other therapeutic options.)

Work with your provider to determine the best alternative for you or your child. 

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