A number of years ago on the recommendation of a veterinary panel, I began feeding spirulina powder to my horse with respiratory allergies. It's been the one thing that really made a difference for her. Now, I've had severe spring and fall allergies for at least 50 years, and since there's no placebo effect in horses I figured it was worth a try for me. I started taking tablets (the powder's pretty nasty tasting stuff) myself in mid-summer and after a few months of spirulina I had no fall allergies, then no spring, and so on. None to speak of since. I have no idea why spirulina has this beneficial effect, but it does. I recommend it!