Hello and welcome to HCM.
Thank you for your query.
I can understand your concern. But the main aspect of your query is the presence of (in your words-bad)
IBS. This makes your gut extremely sensitive to a number of food items, drinks and even medication. Although
spirulina is a nutritional supplement, it can easily have irritated your gut, which is affect with IBS, and resulted in the stinging pain and cramps (which is normally experienced during an episode of IBS).
Please refrain from taking this medication, and if you have been advised any medications for your IBS, then a short course of this medication under the supervision of your doctor should help rid you of the pain and cramps. Usually medications like tricyclic-antidepressants are used to tackle the pain experienced during an episode of IBS. If you wish to initiate a course, then consult your doctor.
I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications at: http://doctor.healthcaremagic.com/doctors/dr-shoaib-khan/64581 . I would gladly help you.
Best wishes.