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Rashes from amoxicillin: Is it a true allergy?

Wellness

Identifying an Amoxicillin Allergy

I had the pleasure of evaluating a 1-year-old female for an amoxicillin allergy. Mother shared her daughter had a cold for a week, but seemed to be getting better. She then developed a fever of 102. She was seen by her pediatrician the next day and was diagnosed with her first ear infection and started on amoxicillin twice a day. 

The patient was starting to get better, but then on the fifth day she woke up with a rash all over and her mother became concerned that her daughter was having an allergic reaction to amoxicillin. Amoxicillin was stopped and her mother has been questioned whether amoxicillin caused a rash or whether it was a more serious allergy. Concerned for her child and unsure about the amoxicillin rash, the mother questioned giving her the medication ever since.

What is Amoxicillin and What is it Used for?

Amoxicillin is a widely prescribed antibiotic that effectively treats bacterial infections in both children and adults. As a member of the penicillin class of medications, amoxicillin works by inhibiting the growth of bacteria, allowing the immune system to efficiently eliminate the infection. It is commonly used to treat a variety of bacterial infections, including those affecting the respiratory tract, ear, nose, throat, urinary tract, and skin.
Doctors often prescribe amoxicillin for conditions such as bronchitis, pneumonia, sinusitis, and strep throat. The medication is available in various forms, including capsules, tablets, chewable tablets, and liquid suspensions, making it accessible and convenient for patients of all ages.
To ensure the effectiveness of the treatment and to prevent antibiotic resistance, it is crucial to follow the prescribed dosage and complete the full course of amoxicillin. Proper adherence to the medication regimen helps to fully resolve the infection and maintain overall health.

About 5 to 10 percent of children taking amoxicillin or Augmentin will develop a skin rash during the course of their medication. Most of these rashes are non-allergic and are typically caused by viruses.

So, how can you tell the difference in amoxicillin rash vs amoxicillin allergy?

Can Amoxicillin Cause a Rash?

Amoxicillin can case a rash as a side effect in both men and women. Having a rash is relatively common amoxicillin side effect and the degree of the reaction can vary in children and adults. An amoxicillin rash can manifest in two forms: allergic and non-allergic. A rash from amoxicillin can last up to a week but typically goes away sooner and how it looks varies on the person and whether it is an amoxicillin allergy or rash.

Amoxicillin rashes can manifest in various forms, including:

  • Maculopapular Rash: Characterized by flat, red patches and raised bumps spread over the body.
  • Hives (Urticaria): Itchy, raised red or skin-colored welts that can change shape and location.
  • Erythema Multiforme: More severe, featuring target-like lesions or bull's-eye shapes with a central red spot, pale ring, and red outer ring.
  • Anaphylactic reaction: This is a rare but severe allergic reaction that includes symptoms like difficulty breathing, swelling of the face, lips, or tongue, hives, and a rapid drop in blood pressure. This reaction requires immediate medical attention.

By staying informed about the potential side effects of amoxicillin, you can take proactive steps to address any adverse reactions and maintain overall health. If you or your child develops a rash while taking amoxicillin, it is crucial to consult with a healthcare provider to determine the cause and appropriate treatment. Understanding these reactions can help manage symptoms effectively and ensure safe use of the medication.

Non-allergic Amoxicillin Rash & Reaction Signs

A non-allergic rash often appears as flat, red spots that may be slightly raised and is generally not harmful. A non-allergic rash occurring while taking amoxicillin or Augmentin will:

  • The amoxicillin reaction may look like small (less than half an inch) widespread pink spots in a symmetrical pattern or slightly raised pink bumps
  • Usually appear on day 5-7 from the start of the amoxicillin or Augmentin, but can occur at any time during the course of the medication
  • It always appears on the chest, abdomen or back and usually involves the face, arms and legs - the rash may worsen before it gets better
  • The rash differs from differs from hives in appearance (hives are always raised, itchy and change location) 
  • Usually goes away in three days, but can last from one to six days 
  • It’s not contagious, so he/she can go back to school

Allergic Reaction to Amoxicillin - Warning Signs

The warning signs that a true allergic reaction is occurring would be sudden onset of the rash within two hours of the first amoxicillin dose, any breathing or swallowing difficulty or very itchy hives. An allergic amoxicillin rash is typically characterized by hives or red, itchy patches and may be accompanied by other symptoms such as difficulty breathing or swelling, indicating a more serious reaction.

Even if you know it’s not an allergic reaction to amoxicillin, it may still feel wrong to continue the medication or give it again in future. There are several reasons why it is better to continue using amoxicillin than stopping or changing to a different antibiotic:

  • Changing to a broader-spectrum antibiotic may not be necessary and could cause other problems, such as diarrhea or vomiting. 
  • Stopping the medication can incorrectly label your child as allergic to the penicillin-family of antibiotics, which would limit future antibiotic choices.

If your child is on amoxicillin or Augmentin and develops a rash, always consult your pediatrician. If considered appropriate by your pediatrician, you can be evaluated by an allergist to assess if future avoidance is needed.

What Causes Amoxicillin Rash or Allergy?

An allergic reaction to amoxicillin, or any other kind of medication, is caused by one’s immune system reacting to that medication as if it were a foreign invader in the body. This reaction most commonly causes a rash known as hives, or whelps, which are itchy, can come and go, and appear in varying parts of the body. This rash typically develops soon after a patient starts to take the medication (within the first 1-2 doses), and may linger for days to weeks.

In contrast, an amoxicillin rash is a flat rash that typically appears several days after starting the antibiotic. This kind of rash always appears on the chest, abdomen, or back, and can also involve the face, arms and legs. What causes this kind of rash is not always apparent, but in some cases the rash is presumed to be caused by a virus. It is not unusual for a child to start with a viral infection, such as a typical cold, and develop a secondary infection, which may be caused by a bacteria. In such cases, amoxicillin may then be given to treat that secondary infection. Viruses can cause skin rashes that appear while one is taking amoxicillin. These rashes are not itchy and can persist for a few days. This kind of rash is not considered to be harmful.

Amoxicillin Rash Treatment

If a true allergic reaction is considered, one should immediately stop taking that medication and discuss with their physician. More severe forms of allergic reaction can cause chest tightness, breathing problems and/or GI symptoms. For hives, giving an antihistamine, such as diphenhydramine (Benadryl) may help relief the itching and calm down the hives.

In contrast, an amoxicillin rash is not considered to be harmful, and — except for observation and patience — there is no treatment for this kind of rash. For this type of rash, it is not necessary to discontinue taking the amoxicillin. An amoxicillin rash is not contagious. Unfortunately, when someone develops such a rash, they may think they are having an allergic reaction and stop taking the medication and consider themselves to be allergic to the medication. This can lead to their physician labeling them as allergic, thus leading to the patient being given different antibiotics — potentially causing more harmful side effects.

Bottom line-if you or your child develops a rash while taking amoxicillin, or any kind of medication, it is best to contact your physician.