The Natural Medicines Comprehensive Database rates the supplements described here as possibly effective. Though the mechanism is often unclear or unknown, some may help by affecting pathways that lead to the synthesis of antibodies key in the allergic response, or by inhibiting allergy-mediating chemicals. Supplements may have side effects, may interact with certain medications or be contraindicated in people with certain conditions. Talk to your health care provider before trying any supplement, especially if you are taking medications, have an immune disorder or are pregnant or breastfeeding.
There is some evidence that the herb butterbur (Petasites hybridus) can decrease nasal inflammation associated with hay fever, comparable to antihistamines. Don't pick and eat butterbur. To be safe, butterbur must be processed to remove its pyrrolizidine alkaloids, which are toxic to the liver. Butterbur may cause a reaction in people who are allergic to plants in the Asteraceae/Compositae family (such as daisies, marigolds, ragweed and chrysanthemums).
Extracts of this plant significantly reduced hay fever symptoms when combined with antihistamines, compared to antihistamines alone, in a 2011 Iranian study published in Otolaryngology—Head and Neck Surgery. Like butterbur, milk thistle may cause reactions in people who are allergic to Asteraceae/Compositae plants.
The Database cites insufficient evidence for the use of stinging nettle, echinacea, vitamin C, capsaicin, cat’s claw, goldenseal, MSM, quercetin and spirulina for treating allergic rhinitis; it is even less enthusiastic about grape seed extract. Other sources have a more favorable view of some of these remedies, including spirulina, quercetin and grape seed extract, citing some evidence of effectiveness—though still not enough to recommend them.
These microorganisms may alter the course of allergic reactions, though studies have not consistently found benefits. In a large 2014 French study, people with grass pollen allergies who took capsules of Lactobacillus paracasei for five weeks reported improvements in quality of life and ocular (but not nasal) symptoms, compared to a placebo group. A 2013 studyfound that Lactobacillus casei reduced cells and chemical mediators associated with nasal inflammation, but did not significantly improve symptoms. The effects of probiotics depend on the type, dose and regimen, and the person taking them.
Better-designed studies are needed to determine the efficacy and safety of dietary supplements for hay fever. Many of the claims being made are based solely on animal or test-tube studies (if even that), or on small clinical trials that are often of poor quality and not replicated. Though there are anecdotal reports of benefits, this may be due to a placebo effect or to the natural fluctuations in symptoms.
Nasal irrigation can help, according to the Natural Standard. It involves pouring saline solution into one nostril and draining it out the other to flush mucus and nasal debris. It is done with a neti pot, bulb syringe or squeeze bottle. A 2012 review of 10 studies found it cut symptoms by 28 percent and drug use by 62 percent. Side effects are minimal—though daily cleansings for a year might lead to sinus infections. There is a rare risk of protozoal meningitis. The Food and Drug Administration (FDA) warns people to use sterile water or water that's been boiled three to five minutes and cooled.