While most chickenpox cases are mild, you should seek immediate medical care if you see signs of serious complications. Go to the hospital if your child has difficulty breathing or a severe, hacking cough, as this could indicate viral pneumonia. Neurological red flags are critical; these include extreme drowsiness or confusion, trouble walking, a severe stiff neck, or a debilitating headache, which are signs of encephalitis (brain inflammation). On the skin, watch for a secondary bacterial infection, signaled by the blisters becoming increasingly red, swollen, warm, and filled with pus, especially if your child develops a fever that returns after initially going away. Finally, signs of significant dehydration, such as no wet diapers or urination for over 8 hours, are also a urgent reason to seek care. Trust your instincts; if your child seems severely ill, don't hesitate.