When Is a good time to blow dry your child’s hair? I have debated and gave great thought to blow drying newly developed hair. Rule #1: Make sure your child isn’t alarmed by the sound of the blow-dryer. The blow-dryer can really harm their ears. A sound that your ears can handle may not be a sound that their ears can handle. Between ages 2 and 6 if a child’s body is still developing so are the ears. Your child also might suffer from mild Hyperacusis which is a child who is sensitive to certain noises.