Can an asthma patient take d mannose(any amount)? Is the d mannose beneficial in asthma conditions in any situation? I am 30yr old, I am suffering from the asthma from quite some time now but I am at a stable condition at this point of time. I want to take the d mannose as per my friends suggestion. But I am skeptical about it. Should I do so, can it be harmful in any way? Would you advise in my condition? What are your opinion about my situation?