The Answer is minimum once a Week. However, India has a tropical Climate so we tend to sweat and produce more body oil throughout the day and night. So, we recommend you change your bed sheets every 4 or 5 days when the temp outside gets warmer.
This Might be a Bit of work but it has its reward.
The fact is, we sweat, we just do, and bedding quickly accumulates dead skin cells and other (well let's just call it stuff). Even if you cannot see the stuff on your sheets, it is there---lurking and sometimes your bed sheets can become smelly.
Allergens are more prolific and more apt to multiply in the warm and humid weather and bedding, in particular, provides a perfect breeding ground for them. Many of us are allergic to dust mites . Dust mites can trigger asthma, hay fever, irritated skin and make you itch.
Washing your bedding at minimum every 7 days is of the utmost importance, especially if you’re allergic to dust mites. Even if you’re not, it’s almost unbearable to think about their droppings where you lay your head 8 hours a night.