Dry Skin vs Dehydrated Skin – How Are They Different?

Dehydrated skin lacks water.
Dry skin lacks oil.

Dry skin is a skin type. A skin type is the type of skin you are born with. You cannot get rid of a skin type. All that you can do, is maintain your skin in good health by looking after it well and by providing your skin with what your skin type lacks.

There are 4 skin types: dry, oily, normal and combination.

Dehydrated skin is a skin condition. A skin condition can be fixed. A skin condition is not specific to a skin type. Anyone, irrespective of their skin type, can have dehydrated skin.

Characteristics of dry skin:

• Dry skin is prone to fine lines, rough patches, inflammation and is flaky. Makeup settles into creases.
• Dry skin usually also becomes dehydrated.
• Dry skin needs products with oil-based ingredients. Dry skin lacks oil. Oils and fats are two main components of the top layer of skin. The skin's top layer acts as a barrier and protects skin from attacks from nasties in the environment. It also stops water from deeper layers of skin from evaporating into the environment. Lack of the right amount of oil compromises the barrier and makes the skin prone to attacks from external allergens and irritants.
  Dry skin craves oil. Products with oil-based ingredients can help dry skin.

Here's a link to a post that talks in detail about how dry skin looks.

Characteristics of dehydrated skin:

• Dehydrated skin can feel stiff. Pinching your skin causes wrinkling. These wrinkles do not look like smile lines or crow’s feet. These wrinkles appear as a network of tiny, triangular fine lines.
• One of the main functions of the top layer of skin is to prevent water from the deeper layers of skin from evaporating into the environment. Dehydrated skin has a weak skin barrier. And so water escapes from deeper layers through the top layer.
  To fix dehydrated skin, you need humectants. Humectants are substances that attract water to the skin. Examples: glycerin, hyaluronic acid, aloe vera.
• Applying a thick cream or facial oil will not help dehydrated skin. What it needs are products that attract water to the skin.