Scales or streaking, crumbling, flaking, and yellow spots on your toenails may be signs that you have a fungal infection.
This can occur from fungi entering your toenail because of its moist environment.
Symptoms may develop slowly. You may get the fungus because of a medical condition like diabetes, exposure to contaminated nail instruments, use of a public place like a swimming pool or locker room, or a skin injury near your toenail.
Nail infections can be very persistent and may require an anti-fungal medication available with a prescription.