[Illness] Prickly Heat [Prevention Pointers] Dress your child in loose-fitting cotton clothing, and have her drink water. If it's extremely hot, stay inside as much as possible. [How To Treat] 
Get your baby or toddler out of the heat right away. Cool colloidal oatmeal baths (brands such as Aveeno are available at drugstores) will relieve the itch and irritation.