Any drug irrespective of nilavembu should not be used for long period without doctor's advice. Nilavembu kudineer choornam is not a single drug but a combination of Nilavembu, Vettiver, Vilamichai vet, Chandhanam, Peypudal, koraikilangu, Chukku, Milagu  and Preparation. While very few companies are genuinly doing as per the classical text,one should ensure that all the above mentioned ingredients are added in equal quantity before consuming. It is largely exploited distributing free of cost without a doctor's supervision. Nilavembu kudineer choornam can be taken as preventive medicine during fever outbreaks for not more than 5 days only when prescribed by a Doctor.This is because ,Ayurveda or Siddha or any Indian system medicine does not follow 'one size fit for all therapy'. Medicines are specifically given according to the individual's dosha imbalance. So please consult with your doctor before taking any medicine. Ask your doctor to examine you.