What causes tears when lying on one's side?

Watery eyes when lying on one's side may be caused by physiological factors or pathological conditions such as allergic conjunctivitis, dacryocystitis, and keratitis. Appropriate management should be chosen based on the underlying cause.

I. Physiological Factors

If the eyes are irritated—for example, by prolonged mobile phone use while lying down or yawning—eye fatigue may result, which commonly leads to tearing when lying on one's side. It is recommended to use the eyes appropriately and maintain a regular sleep schedule.

II. Pathological Factors

1. Allergic Conjunctivitis: Exposure to allergens such as pollen or dust mites can trigger allergic conjunctivitis, causing symptoms like itchy and stinging eyes, often resulting in tearing when lying on one's side. Under medical guidance, medications such as olopatadine hydrochloride eye drops or emedastine difumarate eye drops may be used for treatment.

2. Dacryocystitis: Poor eye hygiene or infections (e.g., by Staphylococcus aureus) may lead to dacryocystitis, causing excessive tearing when lying on one's side. Treatment may include prescribed medications such as tobramycin eye drops or levofloxacin eye drops, or surgical procedures such as dacryocystorhinostomy.

3. Keratitis: Corneal injury or infection by pathogens such as viruses or bacteria can cause keratitis, leading to symptoms like photophobia and tearing. Patients may also experience tearing when lying on one's side. Under medical supervision, treatments may include olopatadine hydrochloride eye drops or acyclovir eye drops.

In addition, other conditions such as blepharitis or the common cold may also cause tearing when lying on one's side. Medical advice should be followed for proper diagnosis and treatment.