It may be what are called "allergic shiners."

From the Mayo Clinic:

Q: What causes black circles under the eyes?

A: Dark circles under the eyes are common but usually not permanent. They're
often due to temporary changes in the blood vessels under the eyes. Fatigue
usually doesn't play a role. Sometimes under-eye darkening is the result of
a chronic skin condition such as atopic eczema. This is more noticeable in
people with darker skin. Under-eye circles can also run in families.

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-MT