By goal
Evidence-Backed Supplements for Allergies & Hay Fever
Sneezing, an itchy runny nose and watering eyes during pollen season push many people to look for supplements that ease allergic rhinitis alongside or instead of antihistamines. The honest picture is that the evidence is moderate at best and aimed at reducing symptoms, not curing the underlying allergy. The strongest case here is Bifidobacterium longum BB536, a well-studied strain with the most consistent data in Japanese cedar-pollen allergy. Vitamin C and N-acetylcysteine have moderate, mostly indirect support through antioxidant and mucus-related effects rather than large allergy-specific trials. Onion earns a mention chiefly as a dietary source of quercetin and organosulfur compounds studied in other contexts, with little direct hay-fever evidence. Probiotics as a category are genuinely mixed: benefit depends heavily on the specific strain. Evening primrose oil (GLA) is the weak one, popular for eczema but not supported by high-quality trials. We grade each option by what human studies actually show. This page is educational and not medical advice; talk to your doctor or pharmacist before starting anything.
| Supplement | Evidence for this goal | Typical dose | Key caution | Studies |
|---|---|---|---|---|
| Bifidobacterium longum BB536 | Moderate | Typically 1x10^10 to 5x10^10 CFU/day for allergy/gut/immune indications… | Very well tolerated with a long history of safe use; FDA GRAS (including infant formula) an… | 10 |
| N-Acetylcysteine (NAC) | Moderate | 600–1,800 mg/day; psychiatric trials often use 2,400 mg/day. | Generally safe. | 21 |
| onion | Moderate | Standard serving: 1 cup chopped, raw (160 g). Eat whole (with skin wher… | High in FODMAPs (fructans), a common trigger of IBS bloating and gas. | 9 |
| Vitamin C | Moderate | 75–90 mg/day RDA; 200 mg saturates tissues. Doses >1g mostly excreted. | Safe. | 21 |
| Evening Primrose Oil (GLA) | Mixed | Commonly 4–6 g oil/day (~320–480 mg GLA). | Generally well tolerated; mild, temporary GI upset is most common. | 16 |
| Probiotics | Mixed | Strain-specific; commonly 1–10 billion CFU/day. Match strain to the stu… | Safe for most. | 19 |