METHOTREXATE SIDE EFFECTS: What is Methotrexate? 🔑A medicine treats cancer and various autoimmune diseases by slowing the growth and activity of said diagnosis. 🔑Methotrexate also treats psoriasis by slowing the growth of skin cells to stop scales from forming. 🔑Methotrexate may treat rheumatoid arthritis and polyarticular juvenile idiopathic arthritis by decreasing the activity of the immune system. 🔑Common Side effects include: loss of appetite, Feeling sick, diarrhea, headaches, etc. 🔑Se