An open, non-randomized pilot study to evaluate adjuvant effects of drops with L. reuteri DSM 17938 + vitamin D3, ingested concomitantly with sublingual immunotherapy (SLIT), in adults with seasonal rhinitis due to Parietaria pollen. 

The product with L. reuteri + vit D3 was ingested during the first month of SLIT (of three in total). Patients’ perceptions of symptom severity and medication use were assessed and  compared in retrospect to the previous pollen season. 15 patients ingested the L. reuteri + vit. D product and 15 were control subjects who received SLIT only. There were significant reductions in symptom severity and use of medications, both within and between groups.

Conclusion: This pilot study suggests that vitamin D3 plus Lactobacillus reuteri DSM 17938 supplementation might improve the effectiveness of a single pre-co-seasonal SLIT course in reducing symptom severity and medication use in patients with seasonal allergic rhinitis.