Using a diffuser for your essential oils is a great way to get benefits through aromatherapy, where you are inhaling the scents. You can either use one oil at a time, or combine them for different effects.
You may have made changes in your life in the past months in the pursuit of improving the strength of your immune system. Increasing super-nutrient foods, getting regular exercise, and getting some time to de-stress are all very important actions for improving the immune system. One way you can boost it even more is to use essential oils.