Does quercetin help with hay fever and allergies?
Quercetin has a clear anti-allergic effect in laboratory research, and a small randomised study in humans shows improvement in hay fever symptoms, but the evidence is still too thin for firm conclusions. If you want to try it, choose a formula with improved absorption and discuss it with your pharmacist.
In laboratory research, quercetin blocks the release of histamine from human mast cells in a dose-dependent manner. It does so at least as effectively as the commonly used anti-allergic drug cromoglycate. In addition, it inhibits inflammation-promoting substances in those mast cells more strongly than cromoglycate does. This mechanism is therefore well supported biologically, but laboratory results say nothing yet about whether it also works in your nose or eyes.
The step towards human evidence is limited. One randomised, placebo-controlled study with 66 adults showed that 200 mg of quercetin per day for four weeks significantly reduced itchy eyes, sneezing, a runny nose and sleep problems caused by hay fever. An important detail: that study used a specially lecithin-bound formula that is absorbed by the intestine more effectively than ordinary quercetin tablets. Whether standard quercetin from the pharmacy does the same cannot be concluded from this research.
A meta-analysis of 13 randomised studies involving a combined 823 participants examined polyphenols (a broader group that includes quercetin) in seasonal hay fever. Nasal symptoms decreased, but the researchers themselves rated the quality of evidence as low to very low, due to inconsistency between studies and risk of bias. Effects on quality of life were not found to be significant.
For skin allergies such as contact eczema and light allergy, there are only small open-label pilot studies without a control group. Those results are too preliminary to draw any conclusions from. Short-term use (four weeks) appears to be safe based on the available studies; too little is simply known about long-term use to say anything meaningful.
If you want to try quercetin for hay fever, there are two practical points to consider. Choose a formula with improved absorption (such as a phospholipid-bound variant), because ordinary quercetin is poorly absorbed by the body. And discuss it with your doctor or pharmacist if you are also using other medication, as interaction data are absent from the available literature.
Evidence is based on laboratory studies (mast cells), one small RCT in humans (n=66), a meta-analysis of polyphenols (rated low to very low quality) and several small open-label pilot studies. No large independent RCTs are available.
Does turmeric help against inflammation?
Curcumin has a biologically plausible anti-inflammatory effect, but the clinical results are mixed. If you want to try it, choose a formulation containing piperine or a liposomal variant, and discuss it with your doctor if you are taking medication.
Does green tea help against infections?
For flu there is reasonable evidence that green tea catechins help; for most other infections the evidence is still limited to laboratory research, so use it as a supplement to conventional prevention, not as a replacement for it.
Does melatonin support your immune system in later life?
Melatonin has clear effects on the immune system in animal and laboratory research, but whether supplements genuinely improve immune function in older people has not been demonstrated. It has long been used for better sleep, which may be indirectly beneficial for immunity.
Does vitamin C actually help against a cold?
Taking vitamin C daily does not protect most people against colds, but does make a cold somewhat shorter and milder. Intensive athletes benefit more. Anyone who really wants an effect during a cold would do better to look at zinc.
Does creatine do anything to your immune system?
Creatine influences immune cells via a specific switch, but whether the outcome is favourable or unfavourable depends strongly on the situation. For boosting immunity or preventing infections, there is too little evidence in humans to recommend it.
Which supplements genuinely support your immune system?
Some supplements genuinely support your immune system, but the effect is greatest when you have a deficiency: so first check whether your vitamin D or zinc levels are adequate, and supplement in a targeted way.