Final answer:
Parents of an 18-month-old child with a febrile seizure should be instructed to give sponge baths with tepid water to manage fever and avoid aspirin due to Reye's syndrome risk.
Step-by-step explanation:
An appropriate strategy to instruct the parents of an 18-month-old child who has just been diagnosed with a febrile seizure and who has a fever greater than 104°F (40°C) is to continue sponge baths with tepid water. It is important to avoid the use of aspirin for children because of the risk of Reye's syndrome, especially if the child may have a viral illness. Additionally, bathing a child with cold water mixed with alcohol is not advised due to potential risks. Dressing the child warmly to prevent chills is unnecessary and may even increase the body temperature further. Using tepid water for sponge baths can help safely reduce the child's fever and is a gentler approach that can be comforting to a child experiencing discomfort from a high fever.