Common side effects of amoxicillin in children are generally mild and manageable. Overall, only a minority of children experience side effects – for instance, about 4–10% of kids treated for ear infections with antibiotics have some adverse effect. Below are typical side effects and guidance on monitoring:
Many children will have mild stomach upset, such as diarrhea, loose stools, nausea, or occasional vomiting. This happens because antibiotics can affect the balance of gut bacteria. These side effects are usually not dangerous. Encourage fluid intake to prevent dehydration if diarrhea or vomiting occurs. Feeding the child yogurt or probiotics during the course (with a doctor’s approval) may help maintain gut flora balance. Monitoring: If diarrhea is severe, persistent, or contains blood, or if vomiting is preventing the child from keeping doses down, contact the healthcare provider. Persistent diarrhea could indicate C. diff infection (even up to 2 months after treatment) and needs prompt evaluation
A skin rash can sometimes occur in children on amoxicillin. Not all rashes mean true allergy. A non-itchy, blotchy pink rash (appearing days into treatment) can occur even when the child isn’t allergic – especially if they have a viral infection like mono, as noted above. This type of rash is usually benign and will resolve after the antibiotic is finished. However, hives (raised, itchy welts) or any rash accompanied by itching, swelling, or trouble breathing may signal an allergic reaction. Monitoring: Caregivers should report any rash to the provider. If it’s just a mild flat rash and the child is otherwise well, the doctor may decide to continue the medication with observation. But stop the medication and seek medical care immediately for hives or any signs of allergic reaction (such as facial swelling or wheezing).
Because antibiotics kill some normal bacteria, children (especially infants and toddlers) might develop yeast overgrowth. This could appear as diaper rash (redness with possible satellite lesions in the diaper area) or oral thrush (white patches in the mouth). These are less common but known side effects due to disruption of normal flora. Monitoring: If a thick diaper rash or mouth sores occur, let the provider know; antifungal treatments might be needed.
Occasionally, amoxicillin may cause headache or dizziness in some children, though these are not very common. Rarely, more serious effects like liver enzyme elevations or hematologic effects (changes in blood cell counts) have been reported, but these are extremely uncommon in short-term use.
Caregivers and pediatric nurses should watch the child’s symptoms to ensure they are improving. Fever and pain should start to improve within 48–72 hours of starting amoxicillin for most infections. If the child is not showing any improvement in about 3 days, or if symptoms worsen at any time, it could mean the bacteria is resistant or the diagnosis may need re-evaluation. In such cases, a follow-up with the provider is warranted to possibly change the treatment. Always ensure the child completes the full course even if they feel better, unless a healthcare professional advises stopping (premature discontinuation can lead to recurrence or resistance).
Adverse effects of amoxicillin mirror those of other β-lactam antibiotics, including nausea, vomiting, rash, and antibiotic-associated colitis; rarer events like neurotoxicity, hepatic injury, and anaphylaxis can occur but are very uncommon.
1 documented effect
Resolves 1–2 days after stopping
Take with food; maintain hydration; consider probiotics (e.g., L. rhamnosus GG)
Report if diarrhea is severe, bloody, or if vomiting prevents oral intake
1 documented effect
Up to one week
Continue if mild; antihistamines or topical steroids per provider
Stop and seek care for hives, swelling, or breathing difficulty
1 documented effect
Until antifungal therapy
Topical antifungals; consider probiotics
Report white patches or diaper rash
1 documented effect
Resolves 24–48 h after discontinuation
Adjust dose in renal impairment; monitor neurological status
Any confusion, agitation, or convulsions warrant immediate evaluation
1 documented effect
Resolves after discontinuation
Monitor labs in chronic conditions; not routinely required for short courses
Baseline and periodic labs if risk factors present
Renal impairment
Age <2 years (higher yeast risk)
Concurrent mononucleosis infection (rash risk)
History of penicillin allergy
Take with food; maintain hydration; consider probiotics (L. rhamnosus GG or S. boulardii at ≥5 billion CFU/day)
📞 Call your pediatrician immediately if you notice any of these symptoms:
Severe, bloody, or persistent diarrhea
Hives, facial swelling, or difficulty breathing
Persistent vomiting preventing oral intake
Signs of C. difficile infection (cramping, mucus in stool)
Unexplained bruising or bleeding
Severe dizziness or pallor
| Effect | Amoxicillin | Amoxicillin-Clavulanate (Augmentin XR) |
|---|---|---|
| Diarrhea | ≈10% | ≈15% |
May potentiate anticoagulant effects
May decrease elimination
Reduces renal excretion, raising amoxicillin levels
May reduce efficacy
Increased risk of rash
Moderate interaction
For babies taking amoxicillin, watch for increased fussiness, changes in eating or sleeping patterns, loose stools, or diaper rash. Most babies tolerate this medication well, and side effects are usually mild and temporary.
Your toddler might develop loose stools or a pink rash while taking amoxicillin. This is common and usually not dangerous. Continue giving the medicine unless we tell you to stop.
Some children get a pink, bumpy rash or stomach upset with amoxicillin. This doesn't mean they're allergic - most rashes are harmless and will go away after finishing the medicine.
Amoxicillin may cause stomach upset or a rash. Most reactions aren't true allergies. It's important to complete the full course to prevent bacteria from becoming resistant to antibiotics.
A: Most amoxicillin rashes are harmless and don't require stopping treatment. Take a photo and call us to describe the rash. We'll help determine if it's safe to continue.
When to validate: Stop immediately and call for hives, facial swelling, or breathing difficulty. For other rashes, call during office hours for guidance.
A: Yes, probiotics like Lactobacillus rhamnosus GG or Saccharomyces boulardii may help prevent diarrhea. Start them with or within 2 days of antibiotics.
When to validate: Discuss with us first, especially for children under 2 or those with serious medical conditions.
A: Mild diarrhea is common and usually not dangerous. Keep your child hydrated. Watch for signs of dehydration: decreased urination, dry mouth, lethargy.
When to validate: Call for severe diarrhea (more than 6 watery stools/day), blood in stool, signs of dehydration, or diarrhea lasting more than 2 days after finishing antibiotics.
A: Fever and pain should start improving within 48-72 hours. Your child should seem more comfortable and have more energy.
When to validate: Call if symptoms worsen at any time or show no improvement after 3 days of treatment.
Clinical assessment framework
Parent and clinician concerns about Amoxicillin