Spirulina and allergic rhinitis

An estimated 10–25% of Western populations have allergic rhinitis (2), usually triggered by allergens such as pollen. Common symptoms are sneezing, nasal itching, watery discharge and congestion.
Avoiding allergens is often impossible. Common treatments include steroid nasal sprays, antihistamines, cromolyn sodium nasal sprays (a mast-cell stabiliser) and immunotherapy. These can be helpful, but some patients still have persistent, frustrating symptoms. Saline nasal irrigation, clearing allergens and mucus debris, may be the best natural treatment option (3,4).
A 2007 Turkish study found that spirulina could reduce allergic rhinitis symptoms (1). Spirulina is a protein- and vitamin-rich blue-green alga used as a supplement, with relatively few studies. In one cited study, a patient taking 2,000 mg/day showed a 32% reduction in interleukin-4 cytokines, potentially relevant to allergic rhinitis (5).
The Turkish double-blind placebo-controlled trial examined spirulina over 21 weeks. It enrolled 150 adults with active allergic rhinitis between June 2006 and February 2007. The source gives the demographic figures as “mean age 58%, 30 women”; these figures are unclear in the original.
Patients with other conditions such as sinusitis, drug-induced rhinitis, nasal deformities and even associated conditions such as asthma were excluded. Participants were asked not to take allergy or rhinitis medicines during the trial.
Patients were randomized to oral spirulina, described as five tablets providing 2,000 mg/day, or five placebo tablets daily for 21 weeks. Identical packs used code numbers to conceal allocation from patients and researchers until the end.
Patients kept weekly diaries of nasal discharge, congestion, sneezing and itching. Each symptom was scored 0 for absent, 1 for mild but not troublesome, 2 for occasionally troublesome, and 3 for severe and troublesome.
Of 150 participants, 129 adequately completed 21 weeks: 85 receiving spirulina and 44 placebo.
The spirulina group consistently improved in all four symptoms compared with placebo. Baseline sneezing scores were similar: placebo 2.84 (SD 0.37), spirulina 2.74 (SD 0.45). At 21 weeks they were 1.91 (SD 0.52) with placebo and 0.58 (SD 0.50) with spirulina. Similar results were recorded for discharge, congestion and seasonal itching. Both groups improved over 21 weeks, possibly through weather changes or placebo effects. Direct comparison nevertheless showed a larger, consistent improvement with spirulina, trending toward no symptoms by study end.
The most striking finding was greater overall treatment satisfaction with spirulina. At the end, patients rated relief from 0 to 10, where 0 meant none. Placebo scored 3.54 ±1.37, versus 7.44 ±0.89 with spirulina (p<0.001).

Researchers concluded that spirulina might be a “clinically effective” option for allergic rhinitis and merits further study to understand its mechanism.