Hydroxyzine works quite differently from the newer antihistamines your child might have taken before. While newer medicines like Claritin or Zyrtec are designed to stay out of the brain and just work on allergies in the body, hydroxyzine is specifically designed to cross into the brain where it can provide both allergy relief and gentle sedation. Think of it as having two jobs: stopping allergic reactions throughout the body and helping your child feel calm and drowsy when they're too uncomfortable to rest. The medication blocks histamine receptors, which are like tiny switches that turn on allergic reactions when they detect something the body thinks is harmful. By blocking these switches, hydroxyzine prevents symptoms like itching, hives, runny nose, and watery eyes. But because it also reaches the brain, it blocks histamine switches there too, which makes children feel sleepy and less anxious. This brain effect is why hydroxyzine is often chosen when a child needs both allergy relief and help settling down for sleep. Interestingly, hydroxyzine gets converted in the liver into cetirizine, which is the active ingredient in Zyrtec. This is why the allergy-fighting effects last longer than the drowsy effects - your child's body is essentially making its own non-drowsy antihistamine from the original medicine. The drowsiness usually lasts 4-6 hours, but the allergy relief can continue for 12-24 hours because of this conversion. This dual action makes hydroxyzine particularly helpful for children who are struggling with severe itching or allergic reactions that are preventing them from sleeping or resting comfortably.