Why are they worser on some days?

[enom]

Basically, I'm wondering why the size is sometimes worse on some days.

Is this to do with water retention? (I'm not overweight in the slightest)

Anyway to prevent it? Sodium/Salt intake?

[rasputin]

Probably due to the temperature. On really warm days they will go puffy as hell, on cold days that might be OK.