When the question of buying Socks comes, I'm always confused about selecting the material (Cotton/ Lycra/ Nylon). From health point of view, are there any guidelines?

Depends on what is happening with your feet. Healthy feet that do not sweat excessively wear what your feel is comfortable.

If you have a problem with your feet then you need to look at the metereals more closly. Such as runners who are prone to blisters should wear synthetic with anti-shear properties. Heavey sweaters need sock with greater wicking properties. Now you even have socks that are anti-odor anti-microbeal and anti-bactereal by impregnating the fiber with certain substances.

Here is an Eww recomandation. If you are dibetic who has poor pain sensation then you should wear white socks that way if your cut your self and bleed you be able to see the stains on your sock just incase you miss the wound by visual inspection.

If you are prone adema the socks that compress and cover the calf with no edge pressure were the sock ends.

Hope this didnot add to the confusion.