Allergies

Itchy, watery eyes are often part of a bigger allergic reaction

Allergic rhinoconjunctivitis, the combination of nasal allergy symptoms with itchy, red, watery eyes, affects up to 40% of people in high-income countries. The gut microbiome is now recognised as a genuine modulator of the immune responses that drive this kind of allergy, through its effects on immune tolerance and the gut's own barrier function.

Tested directly with a real allergen challenge

A randomised, double-blind, placebo-controlled trial gave 166 people with moderate-to-severe grass pollen allergy either a specific multi-strain probiotic, a lower-dose or lower-diversity version of it, or a placebo. Participants were then exposed to grass pollen in a controlled allergen exposure chamber, a setting designed to reliably trigger allergy symptoms. The full-strength, high-diversity probiotic significantly reduced overall symptom scores compared with both its lower-dose version and placebo, showing that the diversity and dose of the bacterial strains used genuinely mattered, not just whether a probiotic was taken at all.

Source: Diversity and Dosage Determine the Efficacy of the Probiotic SYN-53 in Allergic Rhinoconjunctivitis: A Randomized, Double-Blind, Placebo-Controlled Trial

Specific gut bacteria linked to symptom severity

Separate research on allergic rhinitis, which frequently overlaps with the eye symptoms covered here, has found specific gut bacteria, including Butyricicoccus and Eisenbergiella, correlated with symptom severity and quality of life. People with allergic rhinitis also tend to have lower levels of short-chain fatty acids, the beneficial compounds gut bacteria produce by fermenting fibre, than people without allergies.

As with any probiotic, a strain like the one in the trial above only keeps working if it's properly fed. Introducing a helpful strain without also feeding it, and the rest of the gut, with fibre gives it far less chance of maintaining the balance these trials are trying to shift.

Source: Probiotics combined with prebiotics alleviated seasonal allergic rhinitis by altering the composition and metabolic function of intestinal microbiota

What this means for you

Persistent eye itching, redness, or watering during allergy season is worth discussing with a doctor or pharmacist, since standard antihistamines and eye drops remain the established first-line treatment. Given the strength of the trial evidence above, asking about a specific, well-studied probiotic strain as an add-on is a reasonable step, particularly if standard treatments aren't fully controlling symptoms. A varied, plant-rich diet supports the same gut bacteria this research ties to calmer allergic responses. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.