6 reasons why your eye is swollen — from different kinds of infections to allergies

• A stye or a chalazion can cause clogged glands on your eyelids that lead to swelling.
• If your eyes are swollen, itchy, and red, it could be because of allergies to pollen, dust, or other allergens.
• Graves' eye disease is an autoimmune condition that may cause swelling, light sensitivity, and double vision.

When people talk about eye swelling they could be referring to the area around the eye, like the eyelids, or the eye itself. Eye swelling can affect one or both eyes and result in symptoms ranging from discomfort to redness to pain.

There are many potential causes for swelling of the eye and eyelid. The causes can range from very benign issues that will resolve on their own with home care to more serious infections that require urgent medical care.

Here are eight causes of eye swelling:

1. Hordeolum (AKA stye)

A hordeolum is the medical term for a very common eye ailment –– a stye.

"At the base of the eyelashes are oil glands called meibomian glands. These glands can get clogged, leading to a back-up of oil and a swollen bump on the eyelid or even an infection," says Dr. Annie Nguyen, an ophthalmologist with Keck Medicine of USC. 

If a gland gets infected, this results in a stye.

A stye is a small, painful lump that is similar to a small abscess and might have a small spot of pus like a pimple, Nguyen says. Other stye symptoms include: 

• Eyelid swelling
• Eyelid redness or tenderness 
• Crusting around the eye
• Tearing from the eye
• The sensation of having something in the eye 

How to treat it: The main treatment is simple and DIY. Simply apply a warm compress to the area for up to 15 minutes, says Nguyen. 

You can do this a few times throughout the day, or as often as your doctor recommends. In cases where the warm compress isn't enough, your doctor may prescribe you topical antibiotics or administer antibiotics through an injection.

Additionally, Nguyen says to refrain from wearing contact lenses or eye makeup as the area heals.

2. A chalazion

This lump in the eyelid occurs when a gland in your eye gets clogged with oil, says Nguyen. Sometimes, one forms after having a stye. 

"The lump may feel hard without any pus or draining. Sometimes, you may have blurry vision if the lump is large enough to press on the surface of the eye," Nguyen says. There will likely be swelling, redness, and tenderness.

How to treat it: First line of treatment for a chalazion is using warm compresses to attempt to break down the obstruction, says Dr. Vicente Diaz, an ophthalmologist at Yale Medicine and assistant professor of clinical ophthalmology at Yale School of Medicine. 

However, if the warm compresses aren't enough, you may need a steroid injection or a procedure to remove it, says Diaz.

3. Allergies

Allergies can cause the eyelids to swell, and in some cases, the eyes themselves to swell, too, says Nguyen. The medical term for this is allergic conjunctivitis. Nguyen says on top of swelling, you may experience:

• Itching
• Watering or tearing
• Overall irritation and discomfort

This occurs when the immune system has a hyperactive response to an allergen in the indoor or outdoor environment, such as pet dander, dust mites, or pollen. 

In these cases, you will also experience upper respiratory tract symptoms, too, like sneezing or a runny nose. Other times, Nguyen says you may experience an allergic response to products like soap, makeup, or eyedrops. This will result in more localized eye allergy symptoms.

How to treat it: Allergy medications known as antihistamines can help relieve swelling and discomfort caused by allergies, says Nguyen. You can take antihistamines orally as pills or topically as eye drops. To further help with irritation, you can also use artificial tears and cold compresses.

4. Water/fluid retention 

Fluid retention can lead to periorbital edema, or swelling around the eyes, says Nguyen. Typically, the only symptom will be puffiness or swelling surrounding the eyes. 

Nguyen says there are many benign causes of this, including:

• Irregular sleep/lack of sleep
• Crying
• Flying in an airplane
• Consuming too much salt

However, if the swelling lasts for multiple days and you also have significant welling elsewhere in your body, like your hands and feet, Nguyen says this could indicate a more serious overall health condition.

How to treat it: This will typically pass on its own if the cause resolves and as time passes. Cold compresses can help ease swelling, Nguyen says. If the symptoms persist for more than a couple of days, see your doctor.

If you're experiencing swelling in other areas of the body along with other symptoms such as difficulty breathing or heart palpitations, seek medical attention immediately. 

5. Conjunctivitis (Pink Eye)

Pink eye occurs when the conjunctiva –– the lining of the white surface of the eye and inside of the eyelids –– becomes inflamed due to a bacteria (bacterial conjunctivitis) or virus (viral conjunctivitis), Nguyen says. Pink eye symptoms include: 

• Pinkness or redness of the eye
• Yellow or green discharge from the eyes that can get crusty
• Redness and swelling of the eyelids
• Discomfort
• Feeling like you have something in your eye

How to treat it: Nguyen says specific treatment will depend on the underlying cause of the conjunctivitis. If the cause is a bacterial infection, your doctor can prescribe you antibiotic ointments or drops to clear the infection. If the cause is viral, antibiotics will not help and the infection will have to pass on its own, but topical steroid eye drops can ease inflammation. 

In either case, Nguyen says cool compresses and artificial tears can help to relieve your discomfort. Additionally, avoid wearing contacts and using eye makeup, and wash your hands frequently. 

6. Cellulitis

Cellulitis is an infection around the eye. There are two types of cellulitis. If it is pre-septal, Diaz says the infection is more superficial. 

In this case, it's likely that just the skin of the eyelid is inflamed. An orbital cellulitis infection is deeper and even more potentially dangerous. 

In general, the infection spreads quickly and needs medical attention ASAP.

Diaz says cellulitis usually stems from another infection or ailment –– such as starting as a chalazion or extending from a sinus infection.

Some cellulitis symptoms are: 

• Redness and swelling of the eyelid
• Swelling of the tissue around the eye 
• Eye bulging
• Difficulty moving the eye
• Problems with vision
• Fever
• Fatigue

How to treat it: If the infection is pre-septal, oral antibiotics will typically clear the infection, but if the infection is orbital, you may need more intense intravenous (IV) antibiotics, Diaz says. Furthermore, your doctor might need to drain fluid from the area or perform surgery. 

7. Dacryoadenitis

Dacryoadenitis occurs when there is swelling of the lacrimal gland, which is in the upper outer corner of the eye socket, Diaz says. This gland helps produce tears. If you have this condition, the upper eyelid will become very swollen and may get a droopy appearance. 

Aside from the swelling, symptoms of dacryoadenitis include:

• Pain and discomfort when moving the eye
• Eyes watering
• Discharge from the eye
• Redness
• Warmth 
• Lymph node swelling

How to treat it: The treatment will depend on the cause. The root cause of dacryoadenitis could involve an infection or an autoimmune disease, Diaz says. 

If it's caused by a virus, you need antiviral medication. If it's caused by bacteria you need antibiotics. If you have an autoimmune condition that is causing this, your doctor will determine the best course of treatment, and may prescribe a steroid to decrease inflammation. 

8. Graves' eye disease

Graves' eye disease is directly linked to Graves' disease, an autoimmune disease associated with hyperthyroidism, which means your body is producing excessive amounts of thyroid hormone. 

The disease is linked to eye bulging as well as eyelid swelling and puffiness, which usually affects both eyes, Nguyen says. 

Other Graves' eye disease symptoms include: 

• Redness and irritation of the eyes
• Pain or pressure in the eyes
• Difficulty moving the eyes around
• Dry or gritty eyes
• Light sensitivity
• Double vision
• Eyelids that won't close fully

How to treat it: Ultimately, you need to treat the underlying Graves' disease to help with hyperthyroidism. Treatment may involve radioactive iodine therapy or anti-thyroid medications. 

For the eye-specific symptoms, Nguyen says your doctor may prescribe steroids to help with the swelling, and in more severe cases, you may need surgery.

Insider's takeaway

There are many different potential causes of eye swelling, whether it is affecting the eye itself, the eyelid, or both. It's important to take note of any other symptoms you're experiencing to help differentiate one condition from another. 

See a doctor for a proper diagnosis and to receive necessary treatments.