Signs of dry skin:
If your skin feels or looks tight, flaky, or dry and you do NOT experience an oil shine throughout the day at all - summer or winter - then you have dry skin.
Dry skin types generally suffer earlier and more often with fine lines.
Signs of dehydrated skin:
If your skin has been showing signs of tightness, redness, flakiness, sensitivity and irritation lately, but you still experience an oil shine throughout the day at some point, then your skin is not dry, it's dehydrated.
Dehydrated skin is a skin concern caused by a compromised skin barrier that isn't able to retain moisture (water). Dehydration is not a genetic predisposition, like dry skin is.
Dehydrated skin can be a result of environmental assaults, lifestyle (smoking, the consumption of alcohol, sugar or over-processed foods etc) or the use of harsh products on your skin.