Although consumption of dairy products (buttermilk/curd) will help promote restful sleep, prevent breakdown of protein and provide vital nutrients to your body while you have fever
Earlier it was believed they does cause an increase in mucous productions and secretions,if consumed in large quantities during cold
. Latest studies have shown that probiotics (in form of curd/ buttermilk) also help the immune response by both preventing colds and flu
and speeding recovery time.
So go head and consume but practice moderation!