As registered dietitian
Amy Shapiro explained to me, spirulina has been shown to help with heart health, in that it can reduce your bad cholesterol and triglyceride levels, and also decrease blood pressure and prevent artery clogging. It’s also known to be antimicrobial, so it can help promote the healthy bacteria in the gut that prevents the overgrowth of bad bacteria, she added.
I looked for studies on this. I found this:
http://www.umm.edu/health/medical/altmed/supplement/spirulina
Allergic Reactions
Animal and test tube studies suggest that spirulina may protect against allergic reactions by stopping the release of histamines, substances that contribute to allergy symptoms, such as a runny nose, watery eyes, hives, and soft-tissue swelling. But whether these preliminary studies will help people with allergies is not known
It sounds like it may possibly have this effect but that it is not certain.
Will be interested to here from those who give it a try. I use antihistamines daily year round.