A peritonsillar abscess is a pocket of pus that forms in the soft tissue right next to one of your tonsils. It’s the most common deep infection of the head and neck, and it typically develops as a complication of tonsillitis or strep throat that spreads beyond the tonsil itself. The infection creates intense, one-sided throat pain that gets noticeably worse over a few days, often making it difficult to swallow or even open your mouth fully.
Where the Abscess Forms
Your tonsils sit in a small pocket on each side of your throat, held in place by a thin capsule. Between that capsule and the muscles of your throat wall, there’s a narrow potential space. Under normal circumstances, this space is essentially closed. But when infection from a tonsil breaks through the capsule, bacteria can colonize this space and produce a walled-off collection of pus.
Because the abscess pushes the tonsil inward and forward, the swelling is usually visible when someone looks inside your mouth. The soft palate on the affected side bulges noticeably, and the uvula (the small flap hanging at the back of your throat) often gets shoved to the opposite side.
How It Develops
Most peritonsillar abscesses start as a straightforward case of tonsillitis or pharyngitis that doesn’t fully resolve. Bacteria spread from the infected tonsil into the surrounding tissue, first causing inflammation (called peritonsillar cellulitis) and then, if left unchecked, forming a true abscess with a contained pocket of pus. The distinction between cellulitis and a mature abscess matters because cellulitis can sometimes be treated with antibiotics alone, while an abscess almost always needs to be drained.
The bacteria involved are usually a mix of common throat organisms. Streptococcus species are the most frequently isolated aerobic bacteria, with the strep bacteria responsible for strep throat (Group A strep) found in about 23% of aspirate cultures. Anaerobic bacteria, the kind that thrive without oxygen, are equally common and play a significant role in the infection.
Symptoms to Recognize
The hallmark of a peritonsillar abscess is severe, one-sided throat pain. While regular tonsillitis often causes pain on both sides, a peritonsillar abscess almost always affects just one. The pain typically escalates over two to five days and may radiate to the ear on the same side.
Other characteristic symptoms include:
- Difficulty opening your mouth (trismus): The abscess sits right next to the muscles that control jaw movement. As pus accumulates and inflammation spreads, these muscles go into spasm, making it painful or impossible to open your mouth more than a centimeter or two.
- A muffled, “hot potato” voice: The swelling changes the shape of your throat, making you sound like you’re talking with something in your mouth.
- Difficulty swallowing: Many people start drooling because swallowing saliva becomes too painful.
- Fever and general malaise: Temperatures often run high, and you’ll likely feel significantly unwell.
- Bad breath: The bacterial infection produces a noticeable foul odor.
On examination, the soft palate on one side appears swollen and red, the tonsil is pushed toward the midline, and the uvula is displaced to the opposite side. These visual findings, combined with the symptoms above, are often enough for a diagnosis.
How It’s Diagnosed
In many cases, a doctor can diagnose a peritonsillar abscess just by looking inside your mouth and hearing your symptoms. The combination of one-sided swelling, uvular deviation, and trismus is highly suggestive. But when the picture isn’t clear, or when trismus makes it hard to get a good look at the throat, imaging can help.
Ultrasound performed inside the mouth has a sensitivity of 89 to 95% and can reliably distinguish between cellulitis (swelling without pus) and a true abscess. This matters because it can spare you an unnecessary drainage procedure if no pus collection has formed yet. Ultrasound done from the outside of the neck is also effective, with one study in children reporting 100% sensitivity.
CT scans are nearly 100% sensitive, meaning they’re very good at ruling out an abscess when the scan is negative. However, they’re less specific: about 30% of scans read as showing an abscess turn out to have no pus when drainage is attempted. CT is typically reserved for cases where the diagnosis is uncertain, the infection might have spread to deeper spaces in the neck, or the patient isn’t responding to initial treatment.
Treatment: Draining the Abscess
Antibiotics alone rarely resolve a peritonsillar abscess. The standard treatment involves draining the pus, which provides almost immediate relief of pressure and pain. There are two main approaches.
Needle aspiration uses a large needle inserted through the mouth into the abscess cavity to suction out the pus. It’s less invasive, generally less painful, can be done quickly, and doubles as a diagnostic tool (if no pus comes out, the problem may be cellulitis rather than an abscess). The downside is a higher chance of the abscess coming back: recurrence rates in studies range from about 5% to as high as 80% in some small trials, though most fall on the lower end.
Incision and drainage involves making a small cut with a scalpel and then opening the abscess cavity wider with blunt forceps. This breaks up any internal walls dividing the abscess into smaller pockets, creating a wide opening that allows continued drainage. Exposing the inside of the abscess to air also helps kill the anaerobic bacteria that fueled the infection. Recurrence rates with this method range from 0% to 20%, and a Cochrane review found it was associated with a meaningfully lower chance of recurrence compared to needle aspiration. The tradeoff is that it’s more invasive and carries a small risk of injury to surrounding structures.
Both procedures are typically performed under local anesthesia, often right in the emergency department or an ENT clinic. Most people feel dramatic improvement in pain and swelling within hours of drainage.
Antibiotics and Pain Management
After drainage, you’ll be prescribed antibiotics to clear the remaining infection. The antibiotic choice needs to cover both the strep-type bacteria and the anaerobic organisms commonly found in these abscesses. Treatment typically lasts about 10 to 14 days.
A single dose of a steroid given at the time of treatment can help with early recovery. In one clinical trial, patients who received a steroid alongside drainage and antibiotics reported significantly lower pain scores at 24 hours (1.4 out of 10 versus 5.1 in the placebo group). More of them returned to normal eating and daily activities within the first day. By 48 hours, though, the differences between the steroid and placebo groups evened out, suggesting the steroid primarily helps bridge that first painful day after the procedure.
Recovery and Recurrence
Most people improve rapidly after drainage. Throat pain decreases substantially within the first one to two days, and the ability to swallow returns quickly. Trismus takes a bit longer to resolve as the surrounding muscle inflammation settles down, but most people can open their mouth normally within a few days.
The overall risk of developing a second peritonsillar abscess at some point is approximately 10 to 15%. For people who experience recurrent abscesses, or who also have other issues like obstructive sleep apnea or a history of frequent tonsillitis (four or more infections per year), tonsillectomy becomes a reasonable option to prevent further episodes. Tonsillectomy isn’t routinely performed after a single abscess, but it’s considered when the pattern suggests the tonsils will keep causing problems.
Peritonsillar Cellulitis vs. Abscess
These two conditions exist on a spectrum. Peritonsillar cellulitis is the earlier stage: the tissue around the tonsil is inflamed and infected, but no distinct pocket of pus has formed yet. It causes similar symptoms, including one-sided throat pain and swelling, but tends to be less severe. Cellulitis can sometimes be managed with antibiotics alone, without drainage.
The challenge is that the two can look nearly identical on physical exam. Ultrasound is the most practical way to tell them apart, since it can show whether a fluid collection (pus) is present. When ultrasound isn’t available, needle aspiration serves the dual purpose of checking for pus and treating the abscess if pus is found.
Potential Complications
When treated promptly, peritonsillar abscesses resolve without lasting problems. Left untreated, however, the infection can spread into the deeper spaces of the neck, where it becomes far more dangerous. Deep neck space infections can compress the airway, erode into nearby blood vessels, or track downward into the chest. One rare but serious complication is an infection of the jugular vein that can seed bacteria throughout the bloodstream. These complications are uncommon with timely care, but they’re the reason a peritonsillar abscess shouldn’t be treated as just a bad sore throat.