Immune Suppression Medicine

Hi looking for some advice please. Today I got told by my dermatologist that I need to go onto immune Suppression medication as my psoriasis covers ever part of my body from head to toe and red and blue light therapy won't touch it. She gave me a link to look at what the immune Suppression Medicine involves and I'm just really overwhelmed with it all and it's scarred me. Can anyone tell me if you have had this treatment and is it as scary as it sounds would like to hear from people who have gone through this please x