Blue-green algae, particularly Spirulina, has been investigated for its potential benefits in oral health, including the management of gingivitis. Several small studies and pilot trials have explored the use of blue-green algae extracts, often as mouthwashes or topical applications, for their purported anti-inflammatory and antimicrobial effects. The rationale is that blue-green algae contain bioactive compounds such as phycocyanin, chlorophyll, and various antioxidants, which may reduce inflammation and combat oral pathogens implicated in gingivitis.

However, the scientific evidence is limited and generally of low quality. Most available studies are small, short-term, and sometimes lack rigorous controls. For example, some randomized controlled trials have shown reductions in gingival bleeding and plaque scores with Spirulina-containing mouthwashes compared to placebo, but these findings have not been widely replicated or confirmed in larger, well-designed studies.

At present, the use of blue-green algae for gingivitis is not supported by robust scientific consensus. It is not included in major dental or medical guidelines for the treatment or prevention of gingivitis. While there is some preliminary evidence suggesting possible benefits, the overall strength of the evidence is weak (rated 1 out of 5), and more rigorous research is needed before blue-green algae can be recommended for this condition.