One of the methods recommended for using Miracle-Mineral-Supplement to clear up sinus infections, mold or fungus in sinuses is to activate 5-6 drops and inhale the vapors into your sinuses as best you can with shallow breaths, taking care to take a deep breath of fresh air in between. I tried this several times, and although it didn't clear up my sinuses (albeit, NOTHING has been able to clear up my sinuses) I did not have any adverse effects otherwise. Unless your son is huffing the Miracle-Mineral-Supplement vapors like he's sniffing glue, then he should be totally fine.