An allergic reaction, or rash, to amoxicillin can involve papules or hives. It usually clears after stopping amoxicillin. Anyone with an amoxicillin rash needs prompt medical advice, as some reactions can become life threatening.

Amoxicillin is an antibiotic used to treat bacterial infections. Amoxicillin comes from penicillin, which is known to cause allergic reactions in some people.

The drug comes in many different forms, including capsules, tablets, and liquid. One of the common side effects of amoxicillin is a skin rash. An amoxicillin rash can be mild or severe, depending on how sensitive the individual is to the medication.

It can be red or purple and can spread across the body. Amoxicillin rash may also show up as hives, which are red or white bumps that develop on the skin. Or, it may appear as a maculopapular rash with areas that resemble flat, red patches.

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Evidence notes that roughly 1 in 15 people will have an allergic reaction to amoxicillin. In many cases, the allergic reaction is mild and may present as a skin rash.

The type of rash that develops depends on whether the person is experiencing an allergic reaction to amoxicillin or not. Hives can be a sign of an allergic reaction and typically present quickly after ingesting amoxicillin. Hives will typically:

  • appear as raised, red bumps
  • can come and go and change location
  • are usually very itchy

If hives develop after a person takes amoxicillin, it may be because of a penicillin allergy. An allergic reaction can quickly become severe. Anyone who develops hives after taking amoxicillin should seek urgent medical advice.

If breathing difficulties or swelling occur alongside the rash, they should call the emergency services for immediate medical help.

A person may also experience a delayed reaction to amoxicillin that can also present with a rash, known as a maculopapular rash. This rash will usually:

  • appear 3–10 days after a person first takes the medication
  • resemble small, flat, pink spots that appear in a symmetrical pattern
  • begin to fade after 3 days but may take up to 6 days to disappear

In addition to developing a rash, other adverse reactions to taking amoxicillin can include diarrhea, vomiting, and nausea.

Read on to learn more about possible side effects of amoxicillin.

A rash can be a sign of an allergy, so a person should consult a doctor immediately if a rash appears after starting amoxicillin. The doctor may tell them to stop taking the medication. Then, the rash will usually disappear.

A person who develops amoxicillin rash should follow any instructions given to them by their doctor. If the rash disappears by itself, a doctor may recommend finishing the course of medication.

If symptoms worsen or the rash is very itchy, a doctor will likely recommend the person stops taking amoxicillin and takes a different drug instead.

Home and over-the-counter (OTC) remedies

If a rash is itchy, the following may provide relief:

  • applying cooling agents or topical anesthetics
  • applying a cold, wet cloth
  • soaking in a lukewarm oatmeal bath
  • drinking plenty of water to help flush out toxins that are causing the reaction

Read on to learn more about remedies for itchy skin.

A severe reaction

If a person has an allergic reaction to amoxicillin, symptoms could worsen quickly.

If a person experiences an allergic reaction to amoxicillin, they may experience:

Anaphylaxis: Symptoms and what to do

Anaphylaxis is a severe allergic reaction that can be life threatening. The symptoms develop suddenly and include:

  • hives
  • swelling of the face or mouth
  • wheezing
  • fast, shallow breathing
  • a fast heart rate
  • clammy skin
  • anxiety or confusion
  • dizziness
  • vomiting
  • blue or white lips
  • fainting or loss of consciousness

If someone has these symptoms:

  1. Check whether they are carrying an epinephrine pen. If they are, follow the instructions on the side of the pen to use it.
  2. Dial 911 or the number of the nearest emergency department.
  3. Lay the person down from a standing position. If they have vomited, turn them onto their side.
  4. Stay with them until the emergency services arrive.

Some people may need more than one epinephrine injection. If the symptoms do not improve in 5–15 minutes, or they come back, use a second pen if the person has one.

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The dosage of amoxicillin for adults and children varies, depending on what condition it is treating and the form of amoxicillin. The usual strength of amoxicillin capsules are 250 milligrams (mg) and 500mg. Generally, the dosage for an adult is higher than a prescription for a child.

People are usually given amoxicillin orally, by injection, or by intravenous infusion directly into a vein.

Both adults and children can experience either type of amoxicillin rash.

Other known side effects include:

  • dark urine
  • diarrhea or an upset stomach
  • skin blistering or peeling or becoming looser
  • feeling fatigued or weak
  • headache or dizziness
  • difficulty sleeping
  • seizures
  • unusual bleeding or bruising
  • yellowing of the eyes or skin
  • difficulty passing urine or passing less urine than usual

An amoxicillin rash happens due to a drug allergy, or drug hypersensitivity reaction. Skin reactions, such as rashes, are the most common form of allergic drug reaction.

A true allergic reaction to amoxicillin occurs to due an IgE mediated reaction. This refers to when the body responds to antigens of amoxicillin by producing a specific type of antibody called IgE.

This is a type of hypersensitivity reaction that causes an immediate response after exposure to an antigen. When a person experiences a true hypersensitivity reaction to amoxicillin, symptoms usually appear within 30–60 minutes after taking the drug.

However, many people who report an IgE mediated reaction to antibiotics, such as penicillin, do not have a true IgE mediated reaction, and many others with an allergy to amoxicillin may eventually lose their sensitivity.

A person may also experience a non-immediate reaction to amoxicillin, known as non-immediate hypersensitivity. Symptoms of these reactions typically occur more than 1 hour after ingesting amoxicillin. These reactions do not involve antibodies and instead occur due to the drug antigens activating T cells, which are part of the immune system.

The development of amoxicillin rash without any additional symptoms may indicate that the person does not have a true allergy.

As such, it may be helpful for a person to see an allergy specialist, who may recommend skin testing or penicillin challenge to evaluate for a true penicillin allergy.

In other cases, a person may instead develop a rash due to a viral infection. For example, individuals with the condition known as mononucleosis, or mono, who take amoxicillin, are more likely to develop a rash.

Some FAQs about allergic reactions to amoxicillin and amoxicillin rashes can include:

What does amoxicillin rash look like?

The rash can vary in appearance depending on a person’s reaction. A maculopapular rash will resemble small, flat, symmetrical pink spots. However, hives will typically appear as raised, red bumps that may be itchy.

Should I stop taking amoxicillin after developing a rash?

If a person notices a rash after taking amoxicillin, it is advisable they consult a doctor. They will be able to advise whether a person should continue taking the course of medication or whether they should stop.

How do you treat an amoxicillin rash?

Treatment will depend on the symptoms a person experiences. If a doctor advises a person to stop taking amoxicillin, the rash will usually disappear. If the rash is itchy, a person can try remedies such as OTC allergy medication or a lukewarm oatmeal bath.

If a person experiences a severe reaction, they should call emergency services immediately.

Treatment for amoxicillin rash depends on whether the rash is due to an allergic reaction.

In mild cases with no additional symptoms, a doctor may not prescribe any treatment. However, they may advise that a person stops taking amoxicillin. The rash may disappear a few days after a person stops taking the medication.

A person can consider multiple remedies, such as topical anesthetics and a lukewarm oatmeal baths to help manage itchy skin.

If a person develops hives, or experiences any other symptoms associated with an allergic reaction, they should seek immediate medical advice. They may need other treatments to help stop the reaction.