What are the reasons for one tonsil being swollen while the other is not?

Reviewed by Yoshinori Abe, MD

Internal Medicine

One swollen tonsil (unilateral tonsillar enlargement) can be caused by several conditions, ranging from mild to serious:

Infections: Bacterial infections like strep throat, tonsillitis, or a peritonsillar abscess often cause asymmetric swelling.
Benign growths: Cysts, polyps, or stones (tonsilloliths) can enlarge one tonsil.
Serious conditions: In rare cases, unilateral swelling may indicate lymphoma or tonsil cancer, especially if it persists or is painless.

Because the causes vary so widely — from a routine infection to something requiring urgent care — self-diagnosis is unreliable. The fastest way to understand what may be behind your symptoms and what to do next is to take a free, instant, online symptom check. It takes just a few minutes and helps you make an informed decision about seeing a doctor.

Reviewed for medical accuracy: 07/20/2026

Important Next Steps

Learn what’s causing one swollen tonsil Find out if your tonsil swelling needs care See if one swollen tonsil is serious Discover OTC relief for swollen tonsils Find an ear, nose, throat doctor Explore home remedies for swollen tonsils Understand possible causes of swollen tonsils

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Explanation

When one tonsil is bigger than the other, it can be due to several reasons. Sometimes, infections can cause one tonsil to swell more than the other. Infections are common and often not serious.

However, other times, it could be because of growths that are not harmful, like cysts or benign tumors. These growths can make one tonsil appear larger.

In rare cases, a swollen tonsil could be a sign of something more serious, like lymphoma, which is a type of cancer.

If you notice one tonsil is bigger, it's a good idea to check your symptoms to better understand what might be causing the swelling. The doctor can help figure out why one tonsil is swollen and if any treatment is needed.

(References)

Cortez EA, Mattox DE, Holt GR, & Gates GA. (1979). Unilateral tonsillar enlargement. Otolaryngology and head and neck surgery, 530694.
Cinar F. (2004). Significance of asymptomatic tonsil asymmetry. Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery, 15243564.
Berkowitz RG, & Mahadevan M. (1999). Unilateral tonsillar enlargement and tonsillar lymphoma in .... The Annals of otology, rhinology, and laryngology, 10527279.

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