1. "Oily skin does not need to be moisturized." Yes, it does. Dry skin often lacks sebum in the skin and needs both moisture and oil. Oily skin may have plenty of sebum in the skin but still lack moisture. A moisturizing cream creates a barrier that prevents evaporation. Glycerin is an excellent barrier and is therefore found in many skin creams. An oily skin needs cleansing that can wash away excess oils and a moisturizer that mainly contains moisturizing substances, while a dry skin needs milder cleansing that does not wash away too much of the skin's own sebum and a moisturizing cream with a higher content of oils.
2. "Your skin needs collagen."
No, the skin produces collagen itself and this is not something you can add either from the inside or outside. Like so much other cell formation, collagen production decreases with age and therefore wrinkles occur, among other things. You can not affect this production by applying collagen to the skin as these molecules found in collagen creams are too large to penetrate the skin. They do not even go through the stratum corneum, which is the outermost layer of the skin. Likewise, you can not affect collagen production by eating collagen, as this is a protein that will be digested into amino acids in your intestinal tract, like all other proteins you eat.
3. "You can moisturize the skin by drinking water." No, you can not affect the moisture of the skin by drinking water. If you do not suffer from extreme dehydration, it will not show on your skin how much water you have drunk. The body's cells regulate their fluid balance through osmosis and excess water will simply be urinated. If you do not live in a very hot environment or sweat large amounts, you will only need about 1-2 liters of water per day, considering you do not fast or have an extreme diet. Majority of the fluid we ingest actually comes from our diet, (just think how much fluid many vegetables contain). If you do not use a moisturizing cream, moisture will still evaporate from the skin no matter how much water you drink.
4. "The skin absorbs 60% of what smear on the skin." No, the skin does not absorb 60% of what we put on it, in which case it would have been a pretty lousy organ. Most molecules we put on the skin are usually a hundred or several more times too large to even get through the outermost layer of the skin. They may therefore only irritate the skin surface but they do not enter your bloodstream. This is exactly what absorbing means, that is, going through all the layers of the skin and into the bloodstream. There are things that can go into the skin, that is, penetrate the skin, but even this requires that the molecules must be extremely small to get in. Most do not. The percentage of substances that the skin actually absorbs is much closer to the 0% limit than the 100% limit.