Red dry scaly rash all over body mainly on arms and back looks like psoriasis on elbows?

Hard to assess. Rashes are hard to assess when they are not seen in person, but there are some basics you can think about. Things that are localized to a single area are more triggered by a local contact agent as a reaction. If diverse, they are more likely related to food reaction, illness or general contact items (bath soaps, shampoo). If chronic it could be a skin condition like psoriasis. Doc visit needed.