Hello, Uncontrollable hand tremors may not be a side effect of Flonase if she has taken it for a short duration of time. Hand tremors may be indicative of developing neurological disease. It may be due to underlying undiagnosed Parkinson s disease, MS, TBI, stroke, etc. Stress, hyperthyroidism, liver or kidney failure, anxiety, fatigue, etc., also cause tremors. Get clinically examined, get required blood tests, nerve conduction velocity tests, imaging tests done. She should avoid strenuous exercise, avoid alcohol consumption, if diabetic, control blood sugar at all cost. She should get treated underlying diseases like hyperthyroidism, etc. Tremors is commonly treated with anti-seizure medications, anxiety medications, beta blockers, Nerve Up OD, Botox injections, etc. Surgery is recommended if needed. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician