Several studies have shown the positive impact that vegan diet can have on gut microbiota1. At the same time several studies have shown the connections between a gut in a poor status and the occurrence of allergic reactions1,2. Can vegan diet play a role in the reduction (or elimination) of allergic symptoms? Has any study been conducted on this topic?
I assume you are asking about allergies unrelated to foods that are normally excluded from a vegan diet like eggs and dairy. So the question would be whether a vegan diet might reduce symptoms from allergies to non-food items like pollen, dust, mold, animal dander, etc.
An epidemiological study on diet, asthma, and allergies from 2001 showed that young adolescents (age 13-14) had decreased symptoms of wheeze and allergic rhinoconjunctivitis (runny nose, sneezing) associated with increased consumption of cereal and rice, protein from cereals and nuts, starch, as well as vegetables and vegetable nutrients. A more recent meta-analysis from 2017 concludes:
Fruit and vegetable consumption appears to be protective against asthma.
And a recent 2016 publication suggested that high-fibre diets may be beneficial for those suffering from allergies.
... gut microbiome-derived short-chain fatty acids produced from a high-fiber diet have been shown to protect against allergy.
I also came across non-scientific anecdotal evidence of allergy relief after adopting a vegan diet.
I went vegan around March/April last year, so right before summer. I can definitely say that last year my pollen allergy was a lot weaker than it had been the years before.
The evidence is far from conclusive, but it seems safe enough to recommend a diet higher in whole fruits and vegetables (and other foods containing dietary fibre) to somebody looking for ways to mitigate allergy symptoms.
I know i am too late to the party here but I personally have had immense relief from my allergies ever since I turned vegan 8 months ago before which I was a hardcore non vegetarian with some form of meat in every meal
I have severe allergy to dog hair and dander and on playing with my pet Lhasa Apso for even 5-10 minutes used to lead to an allergic outbreak that would require the use of an antiallergy pill (like cetrizine here in India) which would mean me losing out on a day cuz of the sleepiness the pill causes. I had this allergy all my life from a kid to a 27 year old now; spent all my life as this always allergic weakling with a towel in his hand and a red nose
5 months into a strictly vegan diet I first noticed that I hadn't taken the pill in forever and Had been spending long hours with my dogs.. last 60 days of quarantine/lockdown, my pet usually sleeps on my face as its most comfortable there for her and I still haven't had an outbreak!!