What causes unilateral swelling of the face? A comprehensive guide

September 25, 2025 •

4 min read

According to healthcare experts like the Cleveland Clinic, swelling on one side of the face can be triggered by a variety of factors, including dental problems, infections, and allergies. This guide will detail what causes unilateral swelling of the face, providing a thorough overview of the potential culprits and offering guidance on when medical attention is necessary.

Quick Summary

Unilateral facial swelling is commonly caused by localized issues such as a dental abscess, skin infections like cellulitis, salivary gland inflammation (sialadenitis), allergic reactions (angioedema), or trauma to the face, requiring a proper diagnosis to address the root problem.

Key Points

Infections are the top cause: Many cases of one-sided facial swelling stem from localized infections, particularly dental abscesses, cellulitis, or sinus infections.
Allergies can be a culprit: A sudden onset of swelling may be an allergic reaction, such as angioedema, which can be life-threatening if it affects the throat.
Pay attention to location: Where the swelling is centered can indicate the cause, such as a tooth abscess causing jaw swelling or a salivary gland issue affecting the cheek.
Trauma can be a simple explanation: A recent injury to the face, even a minor one, can cause localized swelling and bruising.
Seek immediate care for severe symptoms: Rapidly spreading swelling, difficulty breathing, or high fever with swelling are signs of a medical emergency and require urgent attention.
Not all swelling is serious: While some causes are serious, others like minor bug bites or cysts are less concerning, but a proper diagnosis is still recommended.

Understanding Unilateral Facial Swelling

Unilateral facial swelling, or edema on one side of the face, occurs when fluid accumulates in the tissues. Unlike generalized swelling that affects both sides, one-sided swelling points to a localized problem. The severity and underlying cause can vary widely, from minor issues like a bug bite to serious infections. A proper diagnosis from a healthcare provider is essential for effective treatment.

Infectious Causes

Infections are among the most common reasons for swelling confined to one side of the face. These can originate from various parts of the head and neck.

Dental Infections

Tooth Abscess: This is a pocket of pus caused by a bacterial infection at the root of a tooth. The infection can spread to the jaw and cheek, causing noticeable and often painful swelling on one side of the face. The swelling may be accompanied by severe, throbbing pain, sensitivity to hot and cold, and fever.
Pericoronitis: This is the inflammation and infection of the gum tissue surrounding a partially erupted or impacted wisdom tooth. It can lead to localized swelling, pain, and difficulty chewing.

Skin and Soft Tissue Infections

Cellulitis: A bacterial infection of the deeper layers of the skin and underlying tissue. It causes the skin to become red, painful, and swollen. Facial cellulitis is a serious condition that requires immediate medical attention as it can spread rapidly.
Stye or Conjunctivitis: An infection of the eyelid (stye) or the membrane covering the eye (conjunctivitis) can cause swelling concentrated around one eye that affects the surrounding facial area.

Sinus Infections

Sinusitis: An infection or inflammation of the sinuses. When only one sinus is affected, it can cause pain, pressure, and swelling on that side of the face, particularly around the eye and cheek.

Allergic Reactions

Angioedema: This is a painless swelling of the deeper layers of skin and tissue, often a result of an allergic reaction. It can cause sudden, prominent swelling of the lips, eyes, and cheek. While often harmless, angioedema of the face can become a life-threatening emergency if it involves the throat and airways.
Insect Bites or Stings: A localized allergic reaction to an insect bite on the face can cause immediate swelling at the site of the sting or bite.

Traumatic and Mechanical Causes

Facial Trauma: Any injury to the face, such as a fracture or a bruise, can lead to swelling on the affected side. This includes injuries to the jaw, cheekbone, or nasal bones.
Salivary Gland Issues: Inflammation or blockages in the salivary glands, particularly the parotid gland located in the cheek, can cause localized swelling. This can be caused by an infection (sialadenitis) or a salivary stone (sialolithiasis), which blocks the flow of saliva.
Lymph Node Swelling: Swollen lymph nodes in the neck can cause a lump and swelling that extends up into the jaw and cheek area on one side. This is often a sign of an infection elsewhere in the body.

Other Potential Causes

Some less common but notable causes include:

Cysts or Tumors: A cyst or a benign (non-cancerous) or malignant (cancerous) tumor can cause a localized, persistent swelling on one side of the face. A lipoma, for instance, is a non-cancerous fatty tumor that can appear under the skin.
Nerve Disorders: In rare cases, conditions like trigeminal neuralgia can cause facial symptoms, and while not a primary cause of swelling, related inflammation or secondary issues could occur.

Comparing Causes of Unilateral Facial Swelling


Cause	Onset	Symptoms	Associated Location	Key Identifier
Dental Abscess	Gradual or Rapid	Severe throbbing pain, tooth sensitivity, fever	Cheek, jaw, near an infected tooth	Pain originates from a specific tooth
Cellulitis	Rapid	Red, warm, tender skin; fever, fatigue	Spreads across the facial skin	Expanding area of redness and warmth
Angioedema	Sudden	Painless swelling, welts may be present	Lips, eyes, tongue, face	Rapid onset, often after exposure to an allergen
Salivary Gland Issue	Gradual	Painful lump, dry mouth, foul taste	Cheek, under the jaw, near a gland	Symptoms worsen with eating
Sinus Infection	Gradual	Facial pressure, nasal discharge, headache	Around the eye and cheek	Affects sinuses on one side of face
Trauma	Immediate	Bruising, pain, possible deformity	Site of impact	Clear history of injury

When to Seek Medical Attention

While some causes of unilateral swelling are benign, others require prompt medical evaluation. You should contact a doctor immediately if you experience:

Rapidly spreading or worsening swelling.
Fever, chills, or signs of a serious infection.
Difficulty breathing or swallowing.
Numbness or weakness in the face.
Severe, persistent pain.

Conclusion

Unilateral swelling of the face is a symptom with many potential origins, ranging from common dental issues to serious medical emergencies like angioedema or cellulitis. A careful assessment of accompanying symptoms, such as the location, speed of onset, and presence of pain or fever, can help narrow down the possibilities. Never ignore unexplained facial swelling, especially if it is sudden or accompanied by other signs of infection. Consulting a healthcare professional for an accurate diagnosis and treatment is the safest course of action. For more information on various health symptoms, consider visiting the authoritative Cleveland Clinic website to learn more about facial swelling and other related conditions.

Frequently Asked Questions

Not always. While some causes like angioedema or cellulitis can be very serious, others are less so, such as a mild dental infection or a bug bite. However, because it can be difficult to tell the difference, it's always best to consult a healthcare provider for an accurate diagnosis.

Yes, a sinus infection, or sinusitis, can definitely cause swelling on one side. If only one sinus is affected, you may experience localized pain, pressure, and swelling around the eye and cheek on that specific side.

If a tooth abscess is the cause, you will likely experience severe, throbbing pain in a specific tooth. The swelling often appears on the cheek or jaw near the infected tooth, and you may have fever, tooth sensitivity, or a bad taste in your mouth.

Angioedema is a type of swelling that occurs deeper under the skin, often caused by an allergic reaction. It can cause sudden and sometimes dramatic swelling of the lips, eyelids, or one side of the face. It requires immediate medical evaluation, especially if breathing is affected.

You should go to the emergency room if the swelling appears suddenly or spreads rapidly, if you have difficulty breathing or swallowing, if the skin is hot and red (potential cellulitis), or if you have a high fever.

Yes. Non-infectious and non-allergic causes include trauma (a blow to the face), salivary gland issues like a stone or blockage, certain cysts or benign tumors, and swollen lymph nodes in the neck.

Diagnosis typically involves a physical examination, review of your medical history and symptoms, and possibly imaging tests like X-rays, ultrasound, or CT scans. A dentist may also be consulted to check for dental infections.