From the Dr. Hauschka web site:
Like treats like.
"Though it might seem counter-intuitive to apply oil to an oily complexion, it's actually the most effective solution. The skin knows whether it's sufficiently protected, producing more of its own oil when skin is dry and less when it's balanced. Drying, soap-based products and oil-free acne treatments can rob the skin of its defenses, leaving it vulnerable and triggering the sebaceous glands to produce even more oil. Dr. Hauschka's Normalizing Day Oil provides a light, clean layer of pure plant oils and botanical extracts that calm the skin's oil production while helping to heal and soothe blemishes and irritation.
On the other end of the spectrum we have Moisturizing Day Cream, the activating daily moisturizer that provides hydrating protection in a light, fast-absorbing formula. If we treat dry skin with rich, heavy creams or oils we effectively trick our skin into believing it's been producing too much of its own oil. In response it will decrease production, perpetuating the dry skin cycle. Moisturizing Day Cream is light enough that the sebaceous glands are called upon to gently increase oil production, but provides enough nurturing moisture to prevent dryness and damage. Over time, the skin will regain its balance and be better able to fend for itself."