Amoxicillin Side Effects in Children: What's Normal vs When to Worry
Parent's guide to common reactions and warning signs
Side Effects Overview: How Common Are They?
10-20%
Common
Diarrhea, nausea Continue medication
2-5%
Call Doctor
Rash, vomiting Get medical advice
<1%
Emergency
Severe allergy Go to ER immediately
Common Side Effects (Don't Stop the Medication)
Diarrhea (Affects 10-15% of Children)
Amoxicillin kills good gut bacteria along with the bad, causing loose or watery stools. This is the most common side effect.
What to do: Give probiotics (yogurt with live cultures or probiotic supplements) 2 hours apart from the antibiotic. Keep your child hydrated. This is NOT a reason to stop the medication.
Nausea & Upset Stomach (5-10%)
Mild stomach discomfort, reduced appetite, or feeling "yucky" are common, especially in the first few days.
What to do: Give amoxicillin with food. Smaller, more frequent meals may help. Cold foods are often better tolerated.
Oral Thrush/Yeast (2-5%)
White patches on tongue or inside cheeks. More common after longer antibiotic courses.
What to do: Contact your doctor. They may prescribe antifungal medication. Probiotics can help prevent this.
Amoxicillin Rash: Allergy vs Non-Allergic
Important: Not all rashes are allergies! About 5-10% of children develop a rash while on amoxicillin, but most of these are NOT true allergic reactions.
Non-Allergic Rash (More Common)
Appears 3-7 days into treatment
Flat, pink/red spots that aren't itchy (or only mildly itchy)
Spreads slowly over hours to days
Very common if child has mononucleosis (up to 90%!)
Action: Call your doctor before stopping. They may advise to continue.
True Allergic Rash (Hives/Urticaria)
Appears within minutes to hours of first or second dose
Raised, itchy welts (hives) that come and go
May have swelling
Action: Stop the medication and call your doctor immediately.
Emergency Warning Signs - Go to ER Immediately
Call 911 or go to the Emergency Room if your child has:
Swelling of face, lips, tongue, or throat
Difficulty breathing or swallowing
Hives (itchy welts) appearing within minutes of dose
Extreme paleness or blue-ish color
Becomes unresponsive or very drowsy
Wheezing or stridor (high-pitched breathing)
These symptoms can indicate anaphylaxis, a life-threatening allergic reaction that typically occurs within 30-60 minutes of the first or second dose.
Tips to Minimize Side Effects
1. Probiotics: Give during treatment and for 1 week after. Timing: 2 hours apart from antibiotic dose.
2. Consistent timing: Give every 8 hours exactly (e.g., 8am, 4pm, midnight) for best effectiveness.
3. With food (optional): May reduce stomach upset but not required for absorption.
4. Refrigerate: Store mixed amoxicillin in refrigerator. Shake well before each dose.
5. Complete the full course: Finish ALL prescribed doses even if your child feels better after a few days.
Verify You're Giving the Right Dose
Calculate accurate amoxicillin dosing by your child's weight