Brief Answer:
It can be regurgitant food material

Detailed Answer:
Hello

Thanks for asking on this platform

I can understand your concern. Nexium contains Esomeprazole a potent proton pump inhibitor(acid reducing agent) and is very effective in treatment of reflux disease.
I would suggest you to follow few simple measures to make this treatment more effective
1)Avoid coffee,tea,spicy food and carbonated drinks as this precipitates the reflux
2)Avoid lying down at least one hour after major meal and take meal at least 2-3 hours before going to bed in night
3)Elevate head end of the bed to avoid reflux

If symptom persists even after taking nexium and following all these measures I would like to add some prokinetic(which facilitates the gastric emptying and thus helps in reducing reflux)like cisapride for better relief.

I hope this helps.
Please let me know if you have any more doubts.
Wishing for your child's speedy recovery.
Regards

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