Presently, there has been an increase in the consumption of the blue–green microalga–spirulina (Arthrospira species), which dominates 99.5% of the total world production of microalgae. Primarily sold as a dietary supplement, it is also incorporated into snacks, pasta, cookies, and bread. Owing to its nutrient abundance, spirulina has a variety of potential applications. Extensive studies have been conducted on the health benefits of spirulina, but its safety in terms of allergy has received limited attention. Therefore, to bridge this knowledge deficit, this review aimed to evaluate the allergenic and antiallergic potential of spirulina. In the PubMed and Scopus databases using words related to allergy, we attempted to detect papers on hypersensitivity to spirulina. A total of 128 records were identified, of which 49 were screened. Ultimately, in this review, we analyzed four case studies, encompassing a total of five patients with allergies to spirulina. We assessed the severity of allergic reactions following World Allergy Organization (WAO) Anaphylaxis Guidance 2020, which varied from mild (grade 2) to severe (grade 4) based on the patient’s symptoms. Additionally, our findings indicate that allergy to spirulina is not commonly reported or diagnosed. However, most of the described cases (four of five) regarding allergy to spirulina according to WAO Anaphylaxis Guidance 2020 were classified as anaphylaxis. Furthermore, it is noteworthy that spirulina also possesses antiallergic properties, as evidenced by research studies. Our article delves into both the allergic and antiallergic potential of spirulina.