Here’s the 411 on that painful stye you’ve been dealing with.

Picture this: You wake up, wipe the sleep from your eyes, and head to the bathroom. You flip on the light, look in the mirror, and one puffy eye stares back at you. A swollen eyelid—we’ve all been there.

Most of the time, swollen eyelids are caused by something simple. Maybe you fell asleep without removing your makeup, ate a super salty meal last night, or got bit by a bug. In these cases, a home remedy like a warm (or cold) compress is usually enough to take down the swelling.

But if a swollen eyelid sticks around, you might need to see a doctor to rule out things like infection or an allergy.

Here, experts share the most common reasons your eyelids swell, which ones go away on their own, and which need a doctor’s attention—plus how to prevent puffy eyelids in the first place.

You have a stye

“Think of a stye like an eyelid pimple,” says Ashley Brissette, MD, an ophthalmologist and founder of Daily Practice.

These small, painful red lumps can develop on your eyelid when the meibomian (oil) glands get clogged, she adds.

Styes are typically caused by a bacterial infection, says Y. Claire Chang, MD, a board-certified dermatologist at Union Square Laser Dermatology in NYC. “The resulting inflammation causes redness and swelling,” says Dr. Chang. Sometimes, this swelling can affect the whole eyelid.

Other symptoms of a stye may include the following, per the American Academy of Ophthalmology (AAO):

• A small pus spot at the center of the bump
• Feeling like something is in your eye
• Having a scratchy feeling in your eye
• Being sensitive to light
• Crustiness along the eyelid margin
• Tearing in that eye

How to fix it

Luckily, styes aren’t super serious and tend to go away on their own within a week or two, says Dr. Chang. Try speeding up your recovery time with the following home remedies, per Dr. Chang and Dr. Brissette:

• Use warm compresses: Apply a clean, warm towel on your affected eyelid for about 10 to 15 minutes, three to five times a day. This helps reduce swelling and promote drainage (the stye should pop on its own like a pimple).
• Cleanse the area: Wash the area twice a day with a gentle eyelid cleanser. Adding this step to your daily skin-care routine can also help prevent future styes. Dr.Brissette recommends Daily Practice’s Eye Revive eyelid cleanser ($33), which removes dust, bacteria, pollution, debris, and allergens while hydrating, soothing, and protecting against eye irritation.
• Resist the temptation to squeeze: Like a big zit, styes can get pretty juicy. But popping a stye can worsen the infection. If your stye isn’t improving (or it’s getting worse) with home remedies, you may need to see a doctor. They can drain it properly and/or give you antibiotics if necessary.

You have a blocked oil gland

A blocked oil gland can result in something called a chalazion—a swollen, red bump on the eyelid. If this sounds familiar, it’s pretty similar to styes. The main differences? A chalazion is not usually painful like a stye (it can feel slightly tender, though), per the AAO. Chalazions also tend to develop further back on the eyelid than styes. And unlike a stye, you might have blurry vision if a chalazion grows large enough to press on your eyeball.

How to fix it

You can treat a blocked oil gland the same way you treat a stye: Apply warm compresses, keep the area clean, and don’t squeeze the bump. If your chalazion sticks around, gets worse, or affects your vision, you should head to the doctor’s office. They may prescribe antibiotics, drain it, or give you a steroid shot to reduce the swelling, per the AAO.

You have allergies

Turns out, your eyelids are not immune to the swelling that can happen during an allergic reaction.“When allergens like pollen, dust, pet dander, or certain chemicals come into contact with your eyes,” your immune system may overreact by releasing histamine, says Dr. Brissette.

Histamine is a chemical that plays a big role in your body’s inflammatory response. When it comes to your eyes, histamine leads “to increased blood flow and leaky blood vessels, which cause the accumulation of fluid in the surrounding tissues,” says Dr. Chang. This is what makes your eyelids swollen. And because your eyelid skin is thin and sensitive, swelling can look more noticeable, says Dr. Chang.

Itchiness and redness are also telltale symptoms of an allergy. While environmental allergens like pollen and dust are frequent offenders for swollen, itchy eyelids, other common allergens include foods, medications (like certain antibiotics or preservatives in eye drops), and cosmetics (especially nail polish), according to the Australian Society of Clinical Immunology and Allergy.

A warning to keep in mind: In severe cases, an allergy can cause anaphylaxis, a serious, potentially life-threatening reaction. If you have symptoms like lip and/or tongue swelling or difficulty breathing, seek medical attention ASAP, says Dr. Chang.

How to fix it

Over-the-counter oral antihistamines (like Benadryl, Claritin, and Zyrtec) can help reduce eyelid swelling and other allergy-related symptoms, says Dr. Chang. Cold compresses can also soothe swollen, inflamed eyelids too, says Dr. Brissette. Still, both Dr. Chang and Dr. Brissette agree: The best way to prevent swollen eyelids is to avoid the allergen in the first place. When that’s not totally possible, try cleansing your eyelids daily to remove things like pollen and dust as a preventive strategy.

You have pink eye

You may associate the oozy, crusty puffiness of pink eye with days off in elementary school, but turns out, pink eye can affect adults too. Pink eye, also known as conjunctivitis, is “an inflammation of the conjunctiva—the clear, thin membrane that covers the white part of your eye and lines the inner surface of your eyelids,” says Dr. Brissette.

“This inflammation can lead to fluid retention and swollen eyelids,” says Dr. Chang. Other symptoms of pink eye can include the following, per the Cleveland Clinic:

• Redness
• Tearing
• Yellow, green, or white discharge
• A gritty feeling in your eyes
• Itching
• Burning
• Blurred vision
• Light sensitivity

Pink eye can be triggered by allergens or irritants, but it’s typically caused by a bacterial or viral infection, which is highly contagious and can spread through contaminated surfaces or direct contact with someone who has it, says Dr. Brissette. This is why “it’s particularly common in crowded places like schools and gyms,” she adds.

How to fix it

The course of treatment for pink eye will largely depend on its cause. If it’s from bacteria, antibiotic eye drops should clear it, says Dr. Chang. But if it’s a virus, you’ll have to wait two to three weeks until it goes away on its own, says Dr. Brissette. To ease your discomfort while it heals, try cold compresses for the itchiness, she adds.

It’s also important, like with all germs, to make sure you’re washing your hands throughout the day. Make sure to also wash your pillowcases and towels regularly, and throw away any expired makeup or products you used while infected, says Dr. Brissette.

You have eczema on your eyelid

If your eyelid swelling is accompanied by dry, itchy, or bumpy skin, you might be dealing with eczema. The skin condition can show up anywhere on your body—face and eyelids included. When it does affect your eye area, it can cause redness, flaking, itching, burning, and swelling of your eyelid skin.

Eyelid eczema is most common in people who already have eczema on other parts of their body, says Dr. Chang. It can also show up in people who have reactions to certain allergens or irritants, including the following, per the Cleveland Clinic:

• Skin-care products
• Sunscreen
• Eye drops or contact lens solution
• Fake eyelashes
• Jewelry
• Fragrances
• Glasses
• Latex
• Hair dye
• Pollen or dust mites

How to fix it

When you have an eczema flare, your doctor will likely give you a topical steroid to calm down your angry, inflamed skin. You can also keep eyelid eczema in check by avoiding things that trigger flares, says Dr. Chang.

As a general rule, steer clear of soaps and makeup with fragrance, and use skin products designed specifically for sensitive skin.

You have chronic eyelid inflammation (aka, blepharitis)

Blepharitis is the medical term for irritated, inflamed eyelids. This chronic condition can have multiple causes, but the most common include the following, according to Dr. Chang:

• Seborrheic dermatitis (dandruff on your face that can irritate eyelids and cause inflammation)
• Rosacea (a skin condition that causes redness and inflammation, which can affect your eyelids)
• Eye infections (which can cause inflammation and irritation)
• Allergies (which can trigger irritation)
• Dry eyes (a lack of tears that can lead to inflammation)
• Clogged or malfunctioning oil glands in your eyelids (which can lead to eyelid inflammation and infection)

On top of red, swollen eyelids, other symptoms of blepharitis may include the following, according to the Cleveland Clinic:

• Greasy eyelids
• Red, irritated eyes that itch or burn
• Crusting of eyelashes and eyelid corners, making your eyelids stick together
• Flakes of skin collecting around your eyes and eyelids
• Dry eye or excessive tearing
• Excessive blinking
• Light sensitivity
• Blurred vision
• Loss of eyelashes
• Eyelashes that grow toward your eyes rather than away from them (trichiasis)

How to fix it

The treatment method for blepharitis will depend on what’s causing it. If it’s an infection, antibiotics and/or steroid eye drops will help. If it’s skin-related, like rosacea or eyebrow dandruff, treating these conditions with prescription creams is a smart strategy.

Whatever the root cause, you can also soothe your swollen eyelids with home remedies. The Cleveland Clinic suggests avoiding eye makeup, using warm compresses, getting enough omega-3s for heathy oil glands, and scrubbing your eyelids with spray, foam, or individually wrapped towelettes with hypochlorous acid to reduce dandruff and bacteria.

You’re retaining fluid (aka, edema)

Much like your whole body can hold on to fluid and cause bloating, your eyelids can do the same. This is called edema, and it can give your face an especially puffy appearance. “The eyelids are very thin, so even the smallest amount of swelling looks very prominent here,” says Dr. Brissette.

Lots of things can trigger edema around the eyes. Allergies and high-sodium foods are common culprits, says Dr. Brissette. More serious issues can also cause fluid buildup, including infections, hormonal changes, kidney issues, or heart failure, adds Dr. Chang.

How to fix it

Edema is often a symptom of a larger issue. Once you treat the root cause, swelling should go down. In general, a cool compress can help calm puffy eyelids. Gentle lymphatic massage and sleeping with your head elevated can also reduce fluid retention in the eye region, says Dr. Chang.

“Gentle lymphatic massage and sleeping with your head elevated can also reduce fluid retention in the eye region.” —Y. Claire Chang, MD, dermatologist

You have the herpes virus

Before you panic: Herpes simplex virus (HSV) Type I is actually fairly common. It’s the type that causes cold sores, but it can infect other parts of your face—including your eyelids and eyeballs—and cause swelling, says Dr. Brissette.

While you can technically contract HSV Type 2 (the sexually transmitted form that causes genital sores) in your eyes, Type I is more likely to cause eye infections and spreads to the eyes more easily (think: touching a cold sore and then touching your eye), according to the AAO.

Once you’ve gotten herpes, “the virus can lay dormant in your nerve cells,” says Dr. Brissette. It can be “reactivated” by certain triggers like the following, per the AAO:

• Stress
• Sun exposure or other UV light exposure (such as tanning beds)
• Fever
• Trauma to the body (such as injury or surgery)
• Menstruation
• Certain medications

Herpes in your eyeball even has its own name—ocular herpes, or herpes simplex keratitis. This can cause “inflammation on your eyelids, the conjunctiva (the white of the eye), or the iris (the colored part of the eye),” says Dr. Chang. Symptoms of ocular herpes are usually pain in the eyes, redness, a gritty feeling, light sensitivity, watering, and blisters on your eyelids, she adds.

How to fix it

Herpes (whether in your eye or elsewhere) is manageable with antiviral medications. If you think you have ocular herpes, make an appointment with an ophthalmologist. They will prescribe an antiviral and check that the infection hasn’t spread to other parts of your eye, says Dr. Brissette.

You have a bacterial infection (aka, cellulitis)

Cellulitis is a type of bacterial infection that can happen anywhere on your body, including your eyelids. It can happen when bacteria sneaks through cracks or openings on your skin—like open cuts or wounds, according to the Centers for Disease Control and Prevention (CDC). Sometimes, it can also spread from an infection that starts in your sinuses, per Boston’s Children’s Hospital.

When this happens, cellulitis can manifest in one of two ways: periorbital cellulitis (the area from the skin of your eyelid to the bony area that encloses your eye) or orbital cellulitis (the eye and eye structures within the bony cavity of your face), says Dr. Chang.

Both types can lead to redness, pain, warmth, and swelling of your eyelids, says Dr. Chang. It can also cause blurry vision and widespread symptoms like fever and chills. Luckily, it isn’t contagious, but certain factors do make you more susceptible, per the CDC. You have a higher risk of infection if you:

• Have an injury that causes a break in the skin (like cuts, ulcers, bites, puncture wounds, tattoos, or piercings)
• Have a chronic skin condition (like athlete’s foot or eczema)
• Have had chicken pox and/or shingles
• Use drugs via injection

How to fix it

Dr. Chang says you need antibiotics to treat cellulitis. Catching it early can reduce your chances of more serious complications like meningitis (an infection of the brain and spinal cord), vision loss, and nerve damage, according to Boston Children’s Hospital.

You have thyroid disease

You might know that the thyroid—the tiny, butterfly-shaped endocrine gland in your neck—plays a big part in regulating your metabolism. But you might not know that it can cause some strange eye symptoms when it’s not working well. Thyroid eye disease (TED) is an autoimmune disorder that causes inflammation in your eye muscles and fatty tissue behind your eye, according to Penn Medicine. It can make your eyelids red and swollen, push your eyes out (so they appear to bulge), or even lead to blurred or double vision.

Other signs of TED can include the following, per Penn Medicine:

• Bags under your eyes
• Difficulty moving your eyes
• Dry or watery eyes
• A gritty feeling in your eyes
• Light sensitivity
• Pain in or behind your eye—especially when looking up, down, or sideways

While TED usually affects people with an over-active thyroid (hyperthyroidism), it can also affect those with an under-active thyroid (hypothyroidism) or even in people with a healthy thyroid gland.

How to fix it

Because TED tends to get worse over time, it’s important to see a doctor as soon as you have symptoms. They can check out your eyes and decide which treatment is best for you. For some, simply using artificial tears or taking a selenium supplement (to support thyroid health) might be enough, according to Penn Medicine. But some people with severe TED might need surgery.

You may have shingles

If you’re older than 60, have had chicken pox, or have a weakened immune system, you may have a higher chance of getting shingles, per Penn Medicine. Shingles is like herpes’ cousin: It belongs in the same family of viruses. It’s also the same virus that causes chicken pox, says Dr. Chang.

Like herpes, shingles can lay dormant for years and resurface later on. If it’s activated in your trigeminal nerve (a large nerve in your head), it can cause herpes zoster ophthalmicus—a virus that affects your eyes, says Dr. Chang. Besides swollen eyelids, you can also get one-sided blisters on your eyelids, forehead, or nose, rashes on your shoulders or torso, redness, pain, sensitivity to light, blurred vision, and difficulty moving your eye, she adds.

How to fix it

It’s important to see your doctor right away if you think you have shingles, says Dr. Chang. Your doctor will give you oral or intravenous antivirals to help treat the virus—which can cause vision issues if left untreated. And if you’re older than 50, ask your doctor about getting a shingles vaccine. Older adults who’re vaccinated tend to get fewer complications from the virus, according to Penn Medicine.

In rare cases, it may be eyelid cancer

While not extremely common (especially for those who’re younger and protect their skin from the sun’s rays), a swollen eyelid could signal a serious health issue like cancer. There are many types of cancers that can affect your eyelid, but the most common is a skin cancer called basal cell carcinoma (BCC), according to UT Health San Antonio MD Anderson Cancer Center.

BCCs often appear on your lower eyelid. Besides swelling, other signs to look out for include:

• Discolored (like pink or white) area on the eyelid
• A cut on the eyelid that hurts or bleeds
• Unusual changes to the eyelid’s look or feel
• Lump or bump on the eyelid, especially one that grows

You’re at a higher risk for eyelid cancer if you have light skin or blue eyes, if you’ve spent a lot of time in the sun or exposed to ultraviolet (UV) radiation, or if you smoke cigarettes, per UT Health San Antonio MD Anderson Cancer Center.

How to fix it

The first thing to note is that eyelid cancers like BCC can be treated successfully and don’t usually spread to other parts of your body. But catching it early is key. A dermatologist can check your eyelid and figure out the best kind of treatment—the most common being Mohs micrographic surgery, or the removal of cancerous cells one layer at a time using a microscope, according to UT Health San Antonio MD Anderson Cancer Center.

Protecting your skin from the sun is another important way to prevent skin cancer. Here are a few habits to try, from Stanford Medicine:

• Wear a hat: The bigger, the better. Go for one with at least a 3-inch brim to block the sun’s rays from your eyes and eyelids.
• Try sport sunglasses: Choose lenses that block 99 to 100 percent of UVA and UVB radiation. Bonus if they’re a wraparound type with UV-protective sides.
• Slather on sunscreen: Look for SPF 30 or higher and choose products that are made especially for the eye area (read: non-irritating).

How to prevent a swollen eyelid

You can’t always prevent a swollen eyelid, especially if it’s because of an underlying condition, but you can take steps to help reduce the risk a bit. Here are some tips to try, according to Dr. Chang and Dr. Brissette:

• Avoid possible triggers: Limit your exposure to potential allergens and contact irritants that can cause swelling.
• Always remove makeup and cleanse your eyelids and lashes daily: This helps to remove bacteria, pollen, dust, and other debris, which can lead to infections, allergies, and swelling.
• Use hypoallergenic makeup and skin-care products: These are formulated for sensitive skin and safe for the eye area to prevent eyelid irritation and swelling.
• Wash your hands with soap and water before touching your eyes (or handling your contact lenses): Good hand hygiene helps keep germs and bacteria from getting into your eyes and causing infections.

When to see a doctor

If your eyelid is still swollen after you’ve tried home remedies, or it gets bigger after a few days, it’s time to make a doctor’s appointment. Dr. Chang says to see a doctor ASAP if your swollen eyelid comes with pain, blurry vision, warmth, discharge, or symptoms of infection like fever and chills. These are all signs that you could be dealing with a more serious eye issue.

You should also give your doctor a call if you have any other symptoms like the following, per the National Health Service:

• Your swollen eyelid is red, hot, painful, tender, or blistered
• Your eyelid droops suddenly
• You cannot open your eye or keep it open
• The pain is in your eye (not your eyelid)
• The white of your eye is very red, in part or all over
• You have eye symptoms and a headache or you feel sick
• You’re sensitive to light (photophobia)
• Your eyesight changes (for example, you see wavy flashing lights, zigzag patterns, or colored spots or lines)

And if you already know you have a health condition like thyroid, liver, kidney, or heart disease (or a family history of them), keep an “eye” on your eyes. Any change could be a clue that something else in your body needs to be checked out, says Dr. Chang.