What causes swollen lymph nodes on one side

Swollen Lymph node on One Side of Neck

A tender lymph node on one side of the neck may be due to a number of conditions, varying from minor infection to more severe conditions. Below is an explanation of potential causes and what should be done:

Swollen lymph nodes in neck causes

Infections (most frequent)

• Viral infections: cold, flu, infectious mononucleosis (EBV), COVID-19
• Bacterial infections: strep throat, tonsillitis, dental infection
• Localized infection of the skin around the scalp, ear, or jaw

Tooth or Gum Issues

• Dental abscess or gingivitis may result in swelling of lymph nodes on one side. 

Ear or Throat Infections

• Otitis media (middle ear infection), pharyngitis, or sinusitis.

Injury or Irritation

• Cuts, bites, or shaving irritation over the area may result in reactive lymphadenopathy.

Less Common but Serious Causes

• Tuberculosis (TB) – particularly in endemic areas
• Lymphoma or leukemia – painless, persistent, and progressively enlarging node
• Metastatic cancer – e.g., from head, neck, or lung cancer
• Autoimmune diseases – lupus, rheumatoid arthritis

One Side of Neck Swollen and Painful

Swelling and soreness on one side of the neck—particularly if the swelling is a lump—tends to indicate an inflamed or infected lymph node, but it could be something else. Here's what you need to know:

• Infected Lymph Node (Reactive Lymphadenitis)
• Tonsillitis or Pharyngitis
• Tooth or Gum Infection
• Ear Infection or Mastoiditis
• Abscess (Collection of Pus)

Lump on One Side of Neck

A mass on one side of the neck may have a number of reasons behind it—most are benign, but some need medical care. Here's the division depending on how it feels, if there are other symptoms, and how long it lasts:

Painful lump on side of neck causes

Swollen Lymph Node (Reactive Lymphadenopathy)

• Reason: Infections such as cold, flu, sore throat, dental problems.
• Feels: Soft or rubbery, movable, painful (particularly if recent).
• Usually with: Sore throat, fever, recent illness, ear or toothache.
• Improves in: 1–2 weeks if infection heals.

Cyst (e.g., Sebaceous or Branchial Cleft Cyst)

• Cause: Obstructed gland or congenital defect.
• Feels like: Smooth, rounded, non-tender unless infected.
• May slowly enlarge or become inflamed and red.

Lipoma

• Cause: Accumulation of fatty tissue.
• Feels like: Soft, painless, slow-growing, moveable.
• Not destructive, but may require removal if bothersome.

Abscess

• Cause: Local infection with accumulation of pus.
• Feels like: Tender, red, warm, occasionally fluctuant (fluid-filled).
• Requires: Drainage + antibiotics.

Swollen Neck Gland on One Side

• A tender, movable gland on one side of the neck is usually caused by an infection of a sore throat, a cold, dental condition, or ear infection. 
• The lymph node can be tender to touch, movable, and can be associated with fever or recent illness. 
• Less often, it can be caused by an abscess, tuberculosis, or more severe conditions such as lymphoma or cancer if the lump is hard, painless, and lasts longer than two weeks. 
• Warm compresses, rest, and analgesics may cure it temporarily, but see a doctor if swelling increases, lasts more than two weeks, or is accompanied by weight loss, fever, or swallowing or breathing problems.

Neck Swelling on One Side No Pain

• A painless lump on one side of the neck is usually secondary to an enlarged lymph node, thyroid nodule, cyst, or, in a few instances, a tumor. 
• Without pain, it might not be infectious, particularly if there are no other complaints such as fever or sore throat. 
• Benign causes that are common include lipomas (fatty masses), branchial cleft cysts, or reactive nodes following an acute illness. 
• But if the swelling is hard, persistent, or slowly enlarging, it may be due to a more dangerous condition such as lymphoma or metastatic cancer.

When to worry about swollen lymph nodes in neck?

You need to be concerned about swollen lymph nodes in the neck and consult a doctor if any of the below apply:

Concerning Signs

• Swelling persists for more than 2–3 weeks
• Hard, fixed, or not mobile nodes
• Size greater than 1.5–2 cm and not reducing
• No pain, particularly if prolonged
• Sudden enlargement of the node

Associated with:

• Unintentional weight loss
• Night sweats
• Chronic fever
• Fatigue
• Swallowing or breathing difficulty
• More than one enlarged node in various sites (not only the neck)
• Past history of cancer, TB, or HIV, or if you are in a high-risk group

How to treat swollen neck on one side?

Treatment for a swollen neck on one side is based on the cause. Here's a general plan:

If it's an infection (most common)

• Cause: Sore throat, cold, dental problem, ear infection

Treatment:

• Warm compresses: 15–20 minutes, 2–3 times a day
• Pain killers: Paracetamol or ibuprofen
• Rest and fluid
• Antibiotics: Only if a bacterial infection is diagnosed by a doctor

If it's a cyst or lipoma (non-infectious lump)

• Cause: Sebaceous cyst, branchial cleft cyst, or fatty tissue

Treatment:

• Typically observing
• Surgical excision if large, enlarging, or bothersome

If it's an abscess (collection of pus)

• Appearance: Painful, red, warm, may appear to be fluid-filled

Treatment:

• Drainage by a physician
• Antibiotics

If it's ongoing or potentially serious (e.g., cancer or TB)

• Appearance: Hard, fixed, painless, enlarging lump; weight loss, night sweats

Treatment:

• Immediate medical assessment
• May need biopsy, imaging, or referral to a specialist
• Treatment based on diagnosis (e.g., TB medications, cancer treatment)

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