You never know when set notation is going to pop up. Usually, you'll see it when you learn about solving inequalities, because for some reason saying x < 3 isn't good enough, so instead they'll want you to phrase the answer as the solution set is { x | x is a real number and x < 3 }.
If the skin really looks like the color of ash, a deeper more persistent gray or gray-blue color, this could potentially be due to a side effect of certain medications, with or without interaction from sunlight.
Common Skin Conditions Linked to Pregnancy. Hyperpigmentation: This condition is a darkening of the skin and is caused by an increase in melanin, the substance in the body that is responsible for color (pigment). Pregnancy causes excess melanin production. Melasma (also known as chloasma): Melasma is a form of hyperpigmentation.