According to the American Academy of Dermatology (AAD), more than 85 million Americans are affected by skin diseases each year. But, because of that stigma, there’s not a lot of common knowledge about the even the most prevalent disorders, outside of acne (which tops that list.

To help change that, we spoke with a dermatologist to break down the key facts about four common skin conditions: psoriasis, eczema, rosacea, and seborrheic dermatitis.