Hello. Icy Hot makes several different skin applied products which contain different active ingredients including camphor, menthol, methyl salicylate, and lidocaine. All of these are temporary pain relievers, and as you stated, are directed to be used for children ages 12 years and above. If your 7-year-old child received a single application of any of the above ingredients just once, please rest assured, it will not harm him in anyway. The active ingredients are absorbed locally in to the skin, and will not penetrate the chest or affect his lungs in anyway. I recommend no longer using the product, and if your child has any discomfort, you can use acetaminophen or ibuprofen as needed for pain control.