As for the possible allergies, some people do experience some side-effects when consuming Spirulina, especially if that is the first time they incorporate it to their diet.
The most common side-effects are those due to over-detoxification (it is a good idea to consult your health care provisioner first)
It is good to be aware of any of the following reactions:
1. beta-carotene excess (not worrisome, a yellowish tint in your skin can also happen when you drink too much carrot juice)
2. darker urine and/or frequent bowel movements, usually harmless
3. skin itchiness; consult your health care provider if severe
4. restlessness (take Spirulina powder or supplements in the morning, which is when most of us need an extra boost rather than in the evening)
5. any other unusual reaction that may worry you.