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Flagystatin is a combination of metronidazole
Both the drugs can cause hypersensitivity
eruptions in skin and metronidazole is the cause of your metallic test.
Please have a review to your physician, he may like to add antihistamines to continue current medicines or switch the medicines all together seeing the condition.
I hope this advise would be helpful for you.
Still if you have any queries or doubts, please write me back,
I would be happy to solve them.
Wish you a great health!