Are there any natural or other products that I could give to him to boost his immune system?

There are no products, vitamins, or supplements that have shown to be effective in boosting the immune system in adults or children. It is recommended to focus on non-pharmacological measures such as consuming plenty of fruits and vegetables, getting adequate sleep, managing stress effectively, and practicing good hygiene. In cases of illness, it is important to maintain basic hygiene practices like avoiding close contact, not sharing towels, and washing hands frequently. Additionally, using a saline solution for sinus hygiene can help prevent mucus buildup and reduce the frequency of colds.