What Does It Mean When One Eye Is Swollen? (2024)

There are many causes of eye swelling or puffiness, the most common of which include allergy, a lack of sleep, eating too much sodium, or simple aging. At other times, the swelling (also known as periorbital edema) may be a sign of a potentially serious medical condition like an eye infection, thyroid disease, or diabetes.

Certain clues can point you in the direction of the cause, including whether the swelling involves one eye or both. There may also be accompanying symptoms like itching, a creamy discharge, or breathing problems.

If the swelling is severe or unexplained, an eye specialist like an optometrist or ophthalmologist can help diagnose the cause and prescribe the appropriate treatment.

Symptoms of Swollen Eyes

Periorbital edema refers to the temporary swelling of tissues around the eyes ("peri" meaning around and "orbital" referring to the eyeball) due to fluid retention.

The symptoms of periorbital edema can vary but often include:

• Swelling and puffiness around the eyes
• Eye redness
• Excessive tearing
• Dark circles
• Eye itchiness
• Visible swelling of the sclera (white of the eye)
• Eye pain, either persistent or with eye movement
• Blurred vision or other vision changes
• Sensitivity to light
• Creamy eye discharge

The range of symptoms you experience can suggest the underlying cause. This includes whether the eye swelling is:

• Acute (sudden and severe) or chronic (persistent or recurrent)
• Bilateral (affecting both eyes) or unilateral (affecting one eye only)

Common Causes of Puffy Eyes

The cause of your puffy eyes might be obvious, such as when you've been crying or develop hay fever. But there are also times when the cause of eye swelling is not so clear.

Lack of Sleep

When you stay up late or don't get enough sleep, the breathing patterns you have during a normal sleep cycle—alternating between REM and non-REM sleep—are disrupted. This often leads to sleep-disordered breathing in which abnormal patterns of breathing cause blood oxygen levels to drop.

To compensate for the loss of oxygen, blood vessels will dilate (widen) to deliver more blood to tissues. The dilation, in turn, can cause fluids to leach into surrounding tissues. When the delicate tissues of the lower eyelid are involved, puffiness can ensue.

Sleep apnea, characterized by sleep-disordered breathing, can do the same, making a person not only feel sleepier but look tired during the day.

Diet

Sodium is one of several minerals that regulate the movement of water in and out of cells. When you consume the right amount of sodium in the form of salt, the balance between the water inside and outside of a cell is maintained.

On the other hand, when you eat too much salt, water is not only retained in cells but also starts to accumulate. This is what water retention means.

Sodium is found in high concentration in foods that are both salty and unsalty, including:

• Processed or packaged foods
• Fast food
• Alcoholic drinks
• Carbonated beverages
• Sauces and seasonings
• Lunch meat
• Soups

Limiting foods with a high sodium content may help lower the risk of eye puffiness.

Allergies

Allergies can also cause puffy eyes. These not only include seasonal allergies (hay fever) but also allergies to foods and medications.

Allergies result when exposure to an allergy-causing substance (allergen) triggers the release of histamine into the bloodstream. Histamine is a chemical that induces inflammation, causing blood vessels to swell and leak fluids into surrounding tissues.

When the eyes and nasal passages are involved, puffiness and sneezing can occur. Nasal congestion makes things worse by increasing fluid drainage into surrounding tissues, including around the eyes.

Some of the more common allergens include:

• Dust mites
• Mold
• Pet dander
• Pollen
• Tree nuts
• Peanuts
• Wheat
• Milk
• Soy
• Shellfish

In most cases, these allergies will cause bilateral swelling. However, a bug bite or an allergy-related condition called contact dermatitis can cause unilateral swelling, leaving one eye swollen and the other one not.

Normal Aging

As we age, many parts of our bodies lose muscle tone, firmness, and elasticity. The eyes are no exception.

In most people, the production of collagen (the primary building block of skin, muscles, bones, and connective tissues) starts to dwindle by the late 20s to early 30s, thereafter decreasing at a rate of 1%-1.5% per year.

This not only causes the skin under the eyes to become thin but also undermines the collagen matrix underneath the skin, allowing fat to move into the space. This ultimately results in lower eyelid fat prolapse ("baggy eyes").

With baggy eyes, the laxity and porousness of the skin make them more vulnerable to fluid retention. The accumulated fat beneath the eyes can also readily absorb and retain fluid.

Genetics

It is more than possible to have inherited a tendency toward puffy eyes and dark circles from your parents. If there are several people in your family with puffy eyes, this could even be a sign of a genetic condition that causes puffy eyes.

In rare instances, an inherited disorder like hereditaryangioneuroticedema can cause recurrent episodes of deep tissue swelling(called angioedema). The most commonly affected areas are the face, arms, legs, and airways.

More commonly, genetics is likely to affect how your skin ages and how slowly or quickly collagen production diminishes over time. If, for example, one or both of your parents had baggy eyes in their 20s or 30s, you might have the same at that age.

Medical Conditions Causing Swollen Eyes

There are many medical conditions in which puffy eyes are common. Some of these cause localized inflammation around the eyes, while others cause metabolic changes that affect the fluid balance throughout the body.

Medical conditions that can cause periorbital edema include:

• Blepharitis: Inflammation of the eyelids
• Chalazion: A clogged gland at the base of the eyelashes
• Chronic kidney disease: The gradual loss of kidney function
• Conjunctivitis: Also known as "pink eye"
• Diabetic retinopathy: An eye complication of diabetes
• Keratitis: Inflammation of the clear part of the eye, called the cornea
• Optic neuritis: Inflammation of the optic nerve
• Orbital cellulitis: A severe infection of tissues surrounding the eyeball
• Stye: A minor infection of an eyelash
• Thyroid eye disease: An autoimmune disease that causes eye bulging
  
• Uveitis: Inflammation of the pigmented layer of the eye, called the uvea

Swollen Eyes as a Drug Side Effect

Certain drugs can also cause eye puffiness and the accumulation of fluid under the eye, including:

• Aczone (dapsone)
• Allopurinol
• Anticonvulsants
• Imuran (azathioprine)
• Flagyl (metronidazole)
• Gleevec (imatinib mesylate)
• Minocycline
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Sulfonamides
• Plavix (clopidogrel)

Diagnosing the Cause of Puffy Eyes

Puffy eyes can often be diagnosed through a physical exam and a review of your medical history. Things like hay fever and conjunctivitis ("pink eye") are often self-evident, particularly if you have risk factors for the conditions.

At other times, an extensive investigation may be needed if the symptoms are sudden, severe, or recurrent. This is especially true if the eye puffiness is unilateral and occurs for no apparent reason.

Healthcare providers often suspect certain conditions based on how they typically present themselves. This may start with whether they are typically bilateral or unilateral and whether the symptoms are typically acute or chronic. There are no hard and fast rules.