Homeopathy allows avoiding diseases before they start. Medicines remove the biological tendency to develop the disease. This reduces the risk of common infections, illness and slows down degenerative ageing processes.Apart from any other specific medicine to an illness constitutional medicine is the best preventive medicine. Usually a patient on constitutional medicine does not develop illness and enjoy good health.As times it has been seen that a specific medicine for example Euphrasia taken for conjunctivitis precipitates the illness rather than stimulating the illness. For the same reason it is advisable to take constitutional treatment as a preventive treatment instead of a specific medicine. Eupatorium Perfoliatum is one specific medicine for prevention of chiken gunya fever when taken during epidemic.