If such lines appear on your nails after the age of 40, it’s a clear sign that…

Change in nail color (including the appearance of dark streaks)

Marbled, raised or thickened nails;
pain, swelling or inflammation around the nail

These symptoms can be signs of a fungal infection, trauma, or, in rare cases, melanoma (a serious type of skin cancer that can develop under the nail).
How to care for discolored nails

Here are some simple solutions to reduce the appearance of wrinkles and keep your nails healthy:

Moisturize your hands regularly with a hand and nail cream, especially after washing them.

Make sure to keep your nails well hydrated: dry nails are more likely to crack and break.