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Store at or below 40°F (4°C).
Consume within 3–5 days of opening.
Freeze leftovers if you don’t plan to eat them soon.
Bottom Line
A rainbow sheen on deli ham is usually harmless and a natural result of light on meat. However, always trust your senses—smell, sight, and texture are your best guides to food safety.
If anything seems off, it’s safer to throw it away. When in doubt, don’t risk it—foodborne illnesses aren’t worth a few slices of ham.