TL,DR: yes, but other factors also at play.
Fasting in general coupled with low histamine diet, low carb, staying hydrated by adding salt to my water and drinking that more than other drinks have all helped my allergies / medical conditions.I can’t say for sure which element is the true “active ingredient”, but over the past few years I have had about 2 or 3yrs with very minimal hayfever and eczema, compared to previous yrs where I would have sleepless nights and spend most of my time itching and sneezing if I’m not hermetically sealed away in my bedroom.
Hydrating well, then doing a dry fast helps clear your system quickly if you’ve breached your histamine load.
I think in general, if you want to see improvements in anything, everything else needs to come together correctly. You can’t half ass it.
I can’t drink lots of salted water but then allow myself the “treat” of 4 coffees or an ice cream on top. I gotta be good across the board. Good luck!