Dear Student,
(a) The human haemoglobin is weakly diamagnetic when oxygenated and weakly paramagnetic when deoxygenated thus, using a magnet can improve the blood flow in the underlying tissues and can heal the painful ailments that one suffers from.
(b) Some common side effects could be painful menstrual periods, heavier menstrual periods, nausea , diarrhoea , and fuzzy headedness. Tough these side effects have been observed in some practitioners of magnetic therapy but no conclusive evidence has been found if it was due to the magnets or something else.
(c) Precautions : Pregnant ladies should avoid it. Epileptic people should avoid it. People with pace maker implants should avoid it.
Regards