Hi, Methotrexate belongs to the group of medications known as anti metabolites is used to treat certain types of cancer and to control severe psoriasis and rheumatoid arthritis by decreasing the activity of the immune system that hasn t responded to other treatments. Also, it may be used to control juvenile rheumatoid arthritis. Our immune system helps to change the PH to reduce bacteria in the genital area as well as in the armpits. When Methotrexate inhibits the human body s immune response, the bacteria are allowed to grow. You also secrete more sugar in your sweat when you are immuno-compromised. So, the bacteria has more to feed on. Thus, Methotrexate causes body odour. Again, Methotrexate can cause excess sweat production which may also develop body odour. Take care. Hope I have answered your questions. Let me know if I can assist you further. Regards, Dr. Zubayer Alam, General And Family Physician