Copper mugs are attractive and unusual looking, but they could cause health problems if you don't use them correctly. Under the right circumstances, copper dishware is perfectly safe. Under the wrong ones, it can be toxic.
Acidic foods or long-term storage in an unlined copper mug could be dangerous. The tradition of storing milk in copper containers is a known cause of cirrhosis in Indian children. Never drink juices, tomato-based foods or other sour drinks out of a copper mug.
Copper toxicity comes from consuming too much copper in the diet. This condition may include nausea, vomiting and intestinal problems. Over long periods of time, copper toxicity may cause liver damage, especially in children.
Copper mugs are safe when they have a nontoxic lining or when liquids aren't allowed to remain in the mug for long periods of time. Just drinking from a copper mug won't cause poisoning.