Eccrine gland hyperactivity or hidrocystoma: This condition involves an abnormal increase in sweat production from the eccrine glands, which can be found all over the body, including the face. Hidrocystoma, a type of cyst that forms when eccrine glands become blocked, can also cause localized sweating. The location below the lower eyelid is a common site for these conditions due to the high concentration of eccrine glands in the facial area.

Blepharitis: An inflammation of the eyelids that can cause irritation, itchiness, and excessive tearing, which might be mistaken for sweating. The condition can lead to an overproduction of the eye's natural oils, exacerbating the sensation of wetness or sweating.
Allergic reactions or contact dermatitis: Allergens or irritants can cause an allergic reaction or contact dermatitis around the eye area, leading to symptoms that might include excessive moisture or a sensation similar to sweating due to inflammation and irritation.
Ectopic eccrine gland: A rare condition where eccrine glands are found in unusual locations, potentially causing localized sweating in areas like below the eyelid.

Thyroid ophthalmopathy: Associated with Graves' disease, this condition can cause a variety of eye symptoms, including protrusion of the eyeballs, redness, swelling, and excessive tearing, which might be confused with sweating. It's crucial to identify this condition due to its implications for thyroid health and potential for serious complications.
Lacrimal gland dysfunction: Problems with the lacrimal gland, such as a blockage or tumor, can lead to abnormal tear production, which might be perceived as sweating. Identifying issues with the lacrimal gland is important for preventing complications like dry eye syndrome or vision problems.

Freiberg's disease (idiopathic facial aseptic granuloma): A rare condition that can cause swelling and sweating in the facial area, including around the eyes.
Syringoma: Benign tumors of the eccrine glands that can appear as small, sweat-filled bumps, often around the eyes. While usually harmless, they can cause localized symptoms that might be mistaken for sweating.
Neurological disorders: Certain neurological conditions can affect the autonomic nervous system, leading to abnormal sweating patterns, including in the facial area. These would be rare causes of sweating below the lower eyelid but are important to consider in the differential diagnosis.