1. You have small dents in the surface of your nail.
Small dents on the surface of your nail bed are called pitting, and when they show up with no apparent pattern or reason, this could indicate an autoimmune disorder, conditions in which the body mistakenly starts attacking healthy cells, leading to inflammation.
For example, pitting is typically connected to psoriasis (a skin condition that causes scaly patches to appear on the skin) and psoriatic arthritis (a type of arthritis that commonly affects people with psoriasis). But the phenomenon can also be related to connective tissue disorders like Reiter’s syndrome (a type of arthritis triggered by an infection elsewhere in the body). When pitting shows a regular pattern, it can be a sign of alopecia areata, a type of hair loss caused by an autoimmune response, according to the Mayo Clinic.
If what you’re noticing isn’t quite pitting but is instead deep lines or grooves in your nails, you might be dealing with a phenomenon known as Beau lines. Some lines on your nail can be normal, but Beau lines are noticeably deep and run width-wise on the nail, not vertically. These can appear after really intense stress to your nail makes it stop growing (or grow more slowly than usual) for some time, according to the American Academy of Dermatology Association (AAD). Causes of this can include high fever, which is why there’s been concern about “COVID nails,” or what some experts think may be Beau lines manifesting after COVID-19 infection.