La roche posay is a brand of cosmetic products. Seborrheic dermatitis is an skin condition that can be treated with medications and skin care treatments like la roche posay, it typically affects the face but can also affect all over the body. For people who have a seborrheic dermatitis, it typically causes crusty, scaly or flaky dry rash on the face or any other areas of the body where skin was exposed to many environmental factors such as heat, sun and stress.