What Happens If You Have Strep and Don’t Take Antibiotics?

Most strep throat infections clear up on their own within a week or so, even without antibiotics. The bacteria that cause it, group A Streptococcus, trigger a self-limiting illness in most otherwise healthy people. But “self-limiting” is doing a lot of heavy lifting in that sentence. The reason doctors still prescribe antibiotics for strep is not mainly to shorten your sore throat. It is to prevent a handful of rare but serious complications, some of which can permanently damage your heart, kidneys, or other organs.

The Infection Usually Resolves, but Slowly

A widely held view in European medicine is that strep pharyngitis is a self-limiting disease with low complication rates, and that the benefits of antibiotics are modest enough that some physicians question whether prescribing them is always worthwhile.¹ This does not mean the infection is harmless. It means the sore throat, fever, and swollen glands will usually peak around the second or third day and then gradually improve on their own.

A randomized trial comparing penicillin to placebo in adults with sore throats found that symptoms resolved about one and a half to two days earlier with a full course of antibiotics. In patients specifically confirmed to have group A strep, the advantage was a bit larger, around two and a half days sooner.² So antibiotics make the illness shorter, but the difference is days, not weeks. The placebo group got better too. That gap is real but modest, and it is not the main reason treatment guidelines exist.

Rheumatic Fever and the Heart

The complication that drives most of the urgency around treating strep is acute rheumatic fever. This is not an infection. It is an autoimmune reaction that can start one to five weeks after the throat infection, even after the sore throat is completely gone. The immune system, having geared up to fight the streptococcal bacteria, attacks the body’s own tissues, particularly the heart, joints, and nervous system.³

A meta-analysis of older trials found that without antibiotics, roughly 2.4% of patients with a suspected strep throat infection developed rheumatic fever within one to two months. Among those who took antibiotics, the rate dropped to about 0.7%, representing an almost 70% reduction in risk. In practical terms, you would need to treat about 53 people with antibiotics to prevent one case of rheumatic fever.⁴ Those numbers come from an era when rheumatic fever was more common, and the baseline risk in wealthy countries today is considerably lower. But the math still matters, especially for children and young adults, who are most vulnerable.

When rheumatic fever does strike, the most feared outcome is rheumatic heart disease: permanent damage to the heart valves that can cause regurgitation (blood leaking backward through a valve) or stenosis (a valve narrowing so blood cannot flow through properly).³ This is not a short-term problem. Children and young adults who are genetically susceptible can develop heart valve lesions that require surgery or lead to heart failure years down the road.⁵

By 2015, an estimated 33.4 million people worldwide were living with rheumatic heart disease, and the condition remained a major cause of preventable cardiovascular death, especially in low-income and middle-income countries.⁶ The burden has declined steeply in wealthier nations over the past century, largely because of routine antibiotic treatment for strep. In regions where access to healthcare is limited, rheumatic heart disease still kills tens of thousands of people every year. The highest death rates have been recorded in parts of Oceania, South Asia, and sub-Saharan Africa.⁷

Kidney Complications

A different autoimmune reaction, post-streptococcal glomerulonephritis, can affect the kidneys. This typically appears one to three weeks after a strep throat or skin infection. The immune system forms complexes of antibodies and streptococcal proteins that get trapped in the tiny filtering units of the kidneys, triggering inflammation and acute kidney injury.⁸

Symptoms include blood in the urine (sometimes visible, sometimes only detectable under a microscope), swelling in the face and ankles, and elevated blood pressure.⁹ The good news is that this complication usually resolves on its own, especially in children. The kidneys typically recover fully with supportive care. The catch is that, unlike rheumatic fever, there is less evidence that antibiotic treatment of the preceding strep infection reliably prevents this kidney reaction. The immune response seems to be set in motion before or during the infection itself, and antibiotics may come too late to stop it.

Suppurative Complications and Invasive Disease

Before the autoimmune complications have a chance to develop, the infection itself can spread locally. The most common local complication is a peritonsillar abscess: a pocket of pus that forms next to the tonsil. A review of peritonsillar abscess complications found that the condition could progress to much more dangerous problems, including deep neck infections, an abscess spreading behind the throat or into the chest (mediastinitis), and necrotizing fasciitis, the aggressive tissue-destroying infection sometimes called “flesh-eating disease.” The overall mortality rate among patients with these more serious downstream complications was about 10%.¹⁰

These severe outcomes are rare. Most people with strep never develop an abscess, let alone a life-threatening one. But they highlight the spectrum of what group A strep can do. The same bacteria behind a garden-variety sore throat can, in certain circumstances, cause invasive disease, including streptococcal toxic shock syndrome and bacteremia (bacteria in the bloodstream).¹¹ Reports of highly invasive group A strep infections associated with shock and organ failure have increased since the 1980s.¹² Group A strep infections are normally moderate, but if left untreated, with continued exposure, or with recurring infections, they can lead to fatal outcomes. The bacteria produce a variety of virulence factors and toxins that enable them to cause necrotizing fasciitis, pneumonia, and sepsis.¹³

Scarlet Fever

Scarlet fever is not really a separate disease from strep throat. It is what happens when the particular strain of group A strep you have produces certain toxins that cause a distinctive skin reaction. The hallmarks are a sandpaper-textured rash, a “strawberry tongue” (bright red and bumpy), and fever. It mainly affects school-aged children.¹⁴ Historically, scarlet fever was a feared killer of children. Today it is usually mild with treatment, and even without antibiotics the rash and fever tend to resolve. The concern remains the same as with any strep throat: it is not the acute illness itself that is most dangerous but the autoimmune complications that can follow.

A Possible Link to Neuropsychiatric Symptoms

One of the more unusual and contested areas of strep research involves a possible connection to sudden-onset neuropsychiatric symptoms in children. The idea, often discussed under the label PANDAS (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococci), is that in some children, the autoimmune response to strep may target the brain rather than (or in addition to) the heart.

A large nationwide study found that people with a positive strep test had roughly an 18% higher risk of developing any mental disorder, a 51% higher risk of obsessive-compulsive disorder, and a 35% higher risk of tic disorders compared with people who had not been tested for strep.¹⁵ That is a real statistical association, but the research community remains divided on how to interpret it. Prospective blinded studies have not consistently shown that individual strep infections trigger flare-ups of tics or OCD, and PANDAS remains a diagnosis of exclusion, meaning it is only considered after other explanations have been ruled out.¹⁶ Whether untreated strep increases the risk of these neuropsychiatric outcomes remains an open question.

Why Getting Tested Actually Matters

A sore throat with fever, swollen tonsils, and no cough looks like strep. But a number of viruses can produce almost identical symptoms. Infectious mononucleosis (caused by Epstein-Barr virus) is the classic mimic, and a growing list of other pathogens including cytomegalovirus, adenovirus, and herpes simplex virus can cause a nearly indistinguishable picture.¹⁷ Antibiotics do nothing for any of these viral infections and only expose you to side effects.

Clinical scoring systems exist to help doctors estimate how likely a sore throat is to be caused by strep based on signs like fever, tonsillar exudates, swollen neck glands, and the absence of a cough. But these scores are not very accurate on their own. A meta-analysis found that at high score thresholds, too many true cases are missed, while at lower thresholds, too many people without strep are prescribed antibiotics unnecessarily.¹⁸ A secondary analysis of a randomized trial found poor overall diagnostic accuracy for both the Centor and FeverPAIN scoring systems, with very low sensitivity at higher thresholds.¹⁹ This is why a rapid strep test or throat culture still matters: without lab confirmation, you are guessing, and guessing leads to either unnecessary antibiotics for viral infections or missed treatment for real strep.

The Carrier State

Some people carry group A strep in their throats without any symptoms at all. If you are a carrier and then develop a sore throat from a virus, a positive strep test might make it look like you have bacterial pharyngitis when you actually do not. This distinction matters because carriers face a very different risk profile than people with active strep infections.

The Infectious Diseases Society of America specifically recommends against routine antibiotic treatment of carriers, on the basis that carriers are unlikely to transmit strep to others and face little or no risk of developing complications like rheumatic fever.²⁰ When eradication of carriage is attempted, the evidence for the best approach is limited. A systematic review found that oral clindamycin for ten days was the most effective regimen across the few randomized trials available, outperforming standard penicillin-based options.²¹

Immunity After Infection Is Not Straightforward

You might assume that once you recover from strep, your immune system will protect you against future infections. It does, but only partially and only against that specific strain. Group A strep has more than 200 distinct types, categorized by variations in a surface protein called M protein. Antibodies against one type do not necessarily protect against another. And even against the type you were infected with, immunity is not guaranteed. One longitudinal study found that only about 12.5% of children developed type-specific antibodies after an infection, and some children became reinfected with the same type they already had antibodies against.²²

This incomplete immunity is one reason children get strep repeatedly during their school years, and it is also why developing a vaccine against group A strep has been so difficult. A single infection does not reliably train the immune system, and the sheer diversity of strains makes broad protection hard to achieve.

Where You Live Changes the Equation

Whether skipping antibiotics for strep is a low-stakes or high-stakes decision depends heavily on where you are. In wealthy countries with strong healthcare systems, rheumatic fever has become vanishingly rare. The age-standardized death rate from rheumatic heart disease in 2021 was as low as 0.2 per 100,000 in some countries.²³ In higher-income settings, the risk of any one untreated strep throat leading to rheumatic fever is extremely small. This is part of why many European clinicians take a more cautious approach to prescribing antibiotics for sore throats, weighing antibiotic resistance and side effects against the low probability of a serious complication.

In low-income and middle-income countries, the picture is drastically different. Sub-Saharan Africa has the highest age-standardized incidence and prevalence of rheumatic heart disease globally. South Asia leads in disability-adjusted life-years lost and deaths from the condition.⁷ In these regions, untreated strep infections compound across a population into an enormous cardiovascular burden. The steep decline in rheumatic heart disease in wealthier nations, achieved largely through access to penicillin and improved living conditions, has not been replicated in the global south. For communities without reliable access to diagnosis and treatment, every untreated case of strep carries a meaningful probability of downstream heart damage.

When Delaying Might Be Reasonable

Given that strep throat often resolves on its own and that the main benefit of antibiotics is preventing rare complications, there is an ongoing conversation in medicine about whether a short delay before starting treatment is acceptable. Some guidelines allow for “delayed prescribing,” where a patient receives a prescription but is told to fill it only if symptoms do not improve within a few days. The evidence from older trials suggests that initiating antibiotics within the first nine days of a strep infection still provides protection against rheumatic fever.⁴ This window gives some room for a wait-and-see approach.

The tradeoff is real. Treating everyone who has a sore throat with antibiotics prevents the most strep complications, but it also means giving antibiotics to a large number of people who either have a virus or who would have recovered without problems. One cost-effectiveness analysis found that treating all patients with suspected strep prevented about 90% of streptococcal complications but also led to a high rate of penicillin allergy reactions, most of which occurred in uninfected children. The most cost-effective strategy combined a rapid antigen test with a throat culture, balancing the need to catch real strep infections against the harms of unnecessary treatment.²⁴

In practice, if you are an otherwise healthy adult in a wealthy country and your symptoms are mild, a short delay while waiting for test results is unlikely to change the outcome. For children, for people with a history of rheumatic fever, and for anyone in a community where rheumatic heart disease is still common, the calculation tips strongly toward prompt treatment.