All through 2009 trying to sing made me cough. Dairy product consumption was blamed by some though to be 'cured' meant not one gnats millilitre to be consumed ie anorak vegan. I am a veggie and would rather not bother cows but never attempted this absolution from Dairy and my voice now is maybe better then ever. My singing teacher does recommend avoiding milk when singing, alcohol too till after the show. Only drink water to sing with.
When I went deaf in one ear the pundits blamed Dairy consumption for that too. Old wives tale I reckon.