Difference

• Children should never be given the adult version of Nyquil. The difference between the children and adult versions is not just in dosage; more important is that the children's Nyquil does not contain an ingredient present in the adult version: alcohol.
  
  

Allergic Reaction

• Nyquil contains chlorpheniramine, dextromethorphan and pseudoephedrine as the main ingredients. Though uncommon, allergic reactions to any of the ingredients can happen, especially in very young children who have not been given cold medications before. Call 911 immediately if the toddler should develop hives, breathing difficulties or swelling of any kind.
  
  

Side Effects

• All medication has potential side effects; Children's Nyquil is no exception. Headaches, stomach pains and dizziness are some side effects; the more common ones are dry mouth and drowsiness. Serious side effects include mental confusion, hallucinations, tremors or urination problems; if these occur, stop the medication use and call a doctor immediately.
  
  

Rest

• The calming, sedative effects of the antihistamine in Nyquil should balance out the often hyper effects of the decongestant. Not all children react in the same way. While getting rest is the objective, some children may become more active and even become unable to sleep. This is not cause for alarm but should be noted as a mild side effect in treatment of the common cold.
  
  

Warnings

• Any child who has a history of seizures, thyroid problems, heart disease or high blood pressure should not take Nyquil. While Nyquil is approved for babies 6 months or older, any baby with croup should not be given Nyquil due to the drying effect of the medication.