Aspirin has been linked to Reye's syndrome, a rare but life-threatening illness that can cause swelling in the brain and liver damage, particularly when given to children during a viral infection such as flu or chickenpox. Because of this, guidance in most regions advises against giving aspirin to anyone under 16 for fever or pain.
For children, paracetamol and ibuprofen are the usual recommended options, chosen and dosed according to the child's weight and age. Always check the ingredients of combination cold and flu remedies, as some contain aspirin under other names such as acetylsalicylic acid.
The main exception is when a specialist deliberately prescribes low-dose aspirin for a specific medical condition. In that case, follow the doctor's instructions exactly. Otherwise, keep aspirin out of reach and ask a pharmacist if you are unsure whether a product is safe for your child.