Reishi is not just a super immune booster: it is an ultra immune regulator, so someone with asthma ( such as my husand) or with allergies or any auto immune problem can have their system regulated ( over time; suggested period is 3 months). Duanwood reishi and organic reishi is the best, by far. There are god knows how many studies world wide to back this up. If you have AIDS or cancer, I recc taking this as well as NOW vitamins Mushroom Glyco Nutrients, AHCC powder ( powerful immune booster used in Japan), 4 or more grams of vitamin C powder a day, and eat TONS of turmeric and black pepper together ( turmeric is being studied for its incredible properties and peperine in black pepper boosts its absorbtion). Dr Schultze's Superfood is also a must buy but not available on iherb, and so is the Life Extension Elixir from Ascended Health.