The human face is roughly symmetrical meaning that the vertical half on one side closely matches the other side. It most people it is not a mirror image but very similar. When there is a marked difference between one side of the face compared to the other then it is known as asymmetry. The size and shape of the face of determined by a number of factors, mainly genetics, body weight, general health and age. The structure of the human face is determined by the size, shape and quantity of :
- skull bones (cranium and jaw)
- facial muscles
- subcutaneous fat
- thickness and tautness of the skin
The orientation of the jaw (mandible) in relation to the cranium may also contribute to the shape of the face. Symmetry also applies to the eyebrows, eyes, nose, lips and ears.
Enlarged Side of the Face
Although it is known that the face is symmetrical, there is one side that is slightly larger then the other. This is normal and usually not noticeable unless the face is examined closely. Most people will know which side of their face is slightly larger than the other but it is not noticeable to even close friends and family without careful scrutiny.
Sometimes, however, the enlargement of one side of the face reaches a point where it is clearly evident and even if it does not cause any other symptoms, it can cause psychological stress. One sided facial swelling may occur with a growth in the bone or soft tissue, accumulation of fluid, muscle enlargement, skull bone and particularly jaw displacement compared to the other side of the face. Most of these scenarios are considered to be abnormal and facial asymmetry in these instances needs to be investigated further to identify the cause and corrected. Some of these causes can be potentially life threatening, like a malignant tumor, whereas in other cases it may be uncomfortable but will not lead to severe medical complications.
Why does only one side swell?
The most common causes of one sided facial swelling is a result of inflammation. This is often referred to as soft tissue swelling, although it may involve the bone to some degree as well. In most instances the inflammation is a result of an injury to the face but the inflammation can also arise with infections and allergies. Less commonly there may be one sided swelling of the face due to abnormal tissue growth like a tumor which may either benign (non-cancerous) or malignant (cancerous)
When there is one sided facial swelling, it simply means that the tissue on the enlarged side is affected. Apart from the tissue, each side of its face has its own blood, nerve and lymphatic supply. Therefore a condition that affects these structures on one side will lead to swelling only on that side. If the condition is systemic, or generalized, then both sides may be swollen simultaneously.
Causes of One Sided Facial Swelling
It is important to consider several factors when evaluating the cause of facial swelling which may provide a better indication of the cause.
1. Did the facial swelling start suddenly or develop gradually?
2. Is the affected side painful, tender, numb or experiencing other abnormal sensations?
3. Is the enlarged side hard, soft, spongy or firm?
4. Is the one sides facial swelling affecting speech, breathing, eating or chewing, sense of taste or smell, size of the eyes or eyelid movement?
5. Is the facial swelling isolated to the cheek or extending upwards to the forehead or downwards to the neck?
The most common cause for facial swelling that tends to occur very rapidly and is usually just temporary is an injury to face. In these cases, the cause can be identified to a specific incident. Trauma to the face may occur with :
- Blow to the face, like during an assault.
- Car accidents
- Following dental surgery or other surgical procedures to the face.
- Insect bites and stings
- Chemical burns
- Severe sunburn on one side
- Fractures to the cranium or jaw
The enlargement in these cases is due to fluid accumulation as a result of inflammation. It is the body’s ways of protecting tissue against injury. The blood vessels become leaky allowing excess amounts of fluid from the bloodstream to enter into the tissue spaces. Usually there is also heat of the area, redness, tenderness or pain. If a blood vessel is ruptured due to trauma, there may be an accumulation of blood in the tissue. This is known as a hematoma.
A number of microorganisms can cause an infection on one side of the face. This may be isolated to the superficial layers like the skin and subcutaneous fat, or involve deeper tissue such as the muscle and even extend into the bone. It may be caused by viruses or bacteria which are the most common pathogens, or fungi and other types of parasites. The different types of infections that may cause one sided swelling of the face includes :
- Cellulitis. If this extends to the area around the eye then it is known as orbital cellulitis.
- Abscess – tooth, gingival (gum), peritonsillar.
- Sinusitis which is an infection of the paranasal sinuses.
- Osteomyelitis which is an infection of the skull bone or jaw
- Parotitis which is an inflammation of the parotid gland most commonly caused by an infection like mumps.
- Lymphadenitis which is the inflammation of lymph nodes.
- Eye and eyelid infections like conjunctivitis, keratitis, stye (hordeolum) and blepharitis. The swelling is usually over and around the eye but may extend onto the cheek and up to forehead in severe cases.
There are a number of allergic reactions that can cause one sided facial swelling. The most important and severe is anaphylaxis (anaphylactic reactions) which can be life threatening without immediate medical attention. It usually causes bilateral swelling (entire face swollen). Other allergic causes includes :
- Allergic conjunctivitis
- Allergic rhinitis (hay fever)
- Drug allergies
- Allergies to insect bites and stings
- Allergies to various substances that may be used in facial creams, cosmetics, implants for cheek augmentation and sometimes dental materials.
The facial muscles, like the large masseter muscle, gives the cheeks definition and problems with these muscles can alter the shape and size of the face.
- Atrophy (shrinking) of the muscle on one side as may be seen with partial or complete muscle paralysis (like in Bell’s palsy).
- Hypertrophy (enlargement) of the muscle on one side with clenching on one side or chewing only on one side.
Sometimes facial spasms associated with certain nerve and muscle diseases can cause a facial distortion.
Tumors, either benign (non-cancerous) or malignant (canerous) may arise in any of the following tissues :
- Subcutaneous fat
- Connective tissue
- Lymph nodes or vessels
Less frequently, a tumor or the blood vessels or nerves may also be responsible for the one sided swelling.
Most of the other causes a systemic, meaning that it affects the entire body or several systems of the body simultaneously. It is unlikely to cause one sided facial swelling but instead swelling of the entire face. Nevertheless it is worth considering these conditions as a possible cause of one sided facial swelling.
- Cushing’s disease
- Kidney failure
- Heart failure
- Liver failure
- Serum sickness
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