Unilateral / One Side Facial Swelling (Right, Left Swollen Face)

Both sides of the face are not a mirror image. This means that the shape on one half (right or left side) is not exactly the same as the other half. However, this is not easily distinguished by the naked eye and the differences in most people, although not as subtle as one may think, is usually not a cause for concern. It is not considered to be a deformity and at most impacts on aesthetics as studies have shown that perfectly symmetrical faces are considered to be more attractive.

However, there are instances where there is significant enlargement of one half of the face, or a part of one side. It may due to a mass, skull deformity, soft tissue changes, fluid buildup or swelling which is often a result of inflammation. This unilateral facial swelling needs to be medically investigated to identify the underlying cause. It is a symptoms of some underlying condition and resolves upon effective treatment of the causative condition.

Enlargement of One Half of the Face

An enlargement of one side of the face may not always be serious. It can nevertheless cause significant psychological stress due to the aesthetic impact. The enlargement can be acute where it arises suddenly and can be very severe, often accompanied by other symptoms like pain. It may resolve on its own in a short period of time or after treatment. Alternatively it may be chronic where it develops gradually and persists for long periods of time or even for a lifetime.

Swelling refers to the accumulation of fluid in the tissue spaces as a result of inflammation. Any tissue damage or potential damage to tissue initiates inflammation. It is the body’s response to minimize the extent of the tissue damage. The blood vessels in the area of the the tissue damage becomes leaky. This causes fluid from the bloodstream to enter the tissue spaces and the area enlarges.

When a blood vessel is rupture, blood can also accumulate in the area. An abscess is a collection of pus often associated with an infection and there is often extensive inflammation around the abscess.

Causes of Unilateral Facial Swelling

There are many possible causes of one-sided facial swelling. Trauma, dental problems like a tooth abscess and allergies are more likely to be the acute causes of swelling. When there is severe pain, swelling, difficulty with moving the jaw and facial distortion then it is possible that the skull bone has been fractures. A common long term reason for facial swelling is enlargement of the large cheek muscle, the masseter muscles, which may arise with chronic clenching.


Injury to the face is one of the most common causes of unilateral facial swelling It may be mechanical, electromagnetic or chemical in nature. Mechanical trauma includes blows to the face like with a punch, slamming against a wall, airbag injuries and falls. Electromagnetic is mainly due to prolonged and intense sun exposures as is the case with sunburn. Chemical trauma may occur with exposure to pool acid and similar harsh substances that cause chemical burns.

At times facial swelling may be expected with trauma, like the facial swelling that arises with dental surgery or other maxillofacial surgical procedures. It is usually short-lived and subsides as the wound heals provided there is no post-operative infection or other complications like bleeding. Cold therapy may help relieve acute inflammation due to trauma provided that there is no break in the skin or bleeding.


Allergic reactions arise when the body is sensitive to otherwise harmless substances (allergens). It does not affect every person. When the allergen comes into contact with the skin and causes localized inflammation then it is usually allergic contact dermatitis. However, the allergen can be inhaled or ingested and trigger swelling. With severe types of allergic reactions like anaphylaxis, the swelling may affect the throat and airways as well.

Urticaria is an allergic reaction although the exact allergen is usually not known. It presets with red raised skin lesions and may be accompanied by extensive swelling under the skin known as angioedema. A typical presentation of angioedema is one-sided facial swelling that may even extend to the eyelids and cause it to enlarge from the puffiness. Drug allergies may also cause swelling of the face but it is usually not one-sided.


A number of different infections can lead to one-sided facial swelling, either of the skin, subcutaneous tissues, muscles and fascia or large structures in the area like the parotid gland. Some of the pathogens may enter through a break on the skin, from inside the mouth or with bloodborne infectious agents. Deeper infectious like that of the tonsils or throat usually does not lead to facial swelling on the affected side.

Superficial skin infections like impetigo, deeper infections like cellulitis, abscesses in the parotid gland or within the gums and even bone infections (osteomyelitis) of the skull may all present with one-sided facial swelling. Infections like mumps can cause pronounced parotid gland swelling. Sometimes eye and eyelid infections may also lead to soft tissue swelling on the affected side of the face.


The muscles of the cheek and temples are responsible mainly for moving the jaw up and down when chewing and talking. These muscles of mastication also give shape to the face, especially when it is larger and in people with lower facial fat content. It may be more prominent in some people depending on the shape and location of the cheek bones. These muscles can sometimes become enlarged (hypertrophied) leading to one-sided facial swelling.

Enlargement of the masseter muscle is the most likely to lead to facial swelling. One of the common causes is clenching over a long period of times. The repeated and sometimes constant clenching causes the muscle to go into spasm and enlarge over weeks, months and even years. In some people there may be involuntary contractions and tics with the muscles going into severe and uncontrollable spasms and this can cause facial distortion.

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