Many of us take prescription and over-the-counter medications to prevent, relieve and treat medical conditions, and with those medicines we may expect a few side effects. An upset stomach during antibiotic treatment. Maybe some photosensitivity with acne medication. But some medications come with side effects in an unexpected place: your nails. For example, did you know that the common acne treatment tetracycline may cause yellowing nails in some patients? And that's not all. Another antibiotic, minocycline, may give nails a blue hue. Drugs that contain colloidal silver protein, chemotherapy drugs, and some drugs used to treat HIV and AIDS may all cause nails to darken.