Copper bracelets cause no side effects other than easily reversible discoloration of the skin and, in people with metal allergies, skin irritation.
Occurrences of green wrists due to wearing copper bracelets vary depending on the body chemistry of the wearer and, if desired, are easily washed off. Many expect an occasional green mark to show that the copper is working. Copper combines with sweat, and forms compounds called chelates, which are assimilated by the body. Green deposits occur when chelates are formed faster than they are absorbed.
Copper bracelets discolor the skin as the blue-green copper deposits there. However, this discoloration can be washed away with soap and water over the course of a day or two, and there is no evidence that it harms the skin, though in people with metal allergies, copper can cause dermatitis.
It is assumed that the rate of absorption of copper from a bracelet depends on the condition of the body. In healthy people absorption will be much slower than that of someone in a chronic disease state.
There is no evidence that copper bracelets cause any significant side effects other than discoloring your skin.