Hi, Hydrea is hydroxyurea used for treatment of polycythemia, chronic myeloid leukemia, essential thrombocythemia, sickle cell anaemia etc. It can change to the lungs included fluid on the lung and inflammation causing shortness of breath or trouble breathing and cough. Again, it can allergic reaction like rash, hives, itching, wheezing, tightness in chest, shortness of breath, swelling of mouth, face, lips, tongue and throat. It can reduce the white blood cell counts and makes the body more vulnerable to develop Infections. Thus increases the chance of respiratory tract Infections and breathing difficulties. It has effects on brain and develop central neurotoxicity or commonly known as brainfog .It can cause confusion, cognitive problems, memory loss, lack of sharp focus, disrupts balance and movement, dizzy spells etc. Other side effects are fever, bodyache, nausea, vomiting, back pain, joint pain, diarrhea, constipation, vertigo, fatigue etc. If you want, you can contact with your hematologist. 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,