What Causes Scarlet Fever and What Are the Long-Term Effects?

What is scarlet fever?

Scarlet fever is caused by group A Streptococcus. If the bacteria attack your throat, it's called strep. If it gives you a skin rash, it's scarlet fever.

Scarlet fever, or scarlatina, is a bacterial infection that typically affects children and teenagers. It’s caused by a type of bacteria called group A Streptococcus, or group A strep. If the bacteria attack your throat, it’s called strep. If it gives you a skin rash, it's diagnosed as scarlet fever.

Only 10% of people who are exposed to group A strep develop scarlet fever. The bacteria creates a toxin that reacts with your skin, resulting in a scarlet-colored rash that has the texture of sandpaper.

Symptoms of scarlet fever

Early symptoms of scarlet fever include a fever and sore throat. Typically, the rash first appears on your neck and chest, then spreads to the rest of your body.

When making a diagnosis, your doctor will pay more attention to the texture of the rash instead of the color. The rash can last for a week or even longer. As it fades, the skin on your fingertips, toes, and groin area may start to peel.

Other symptoms of scarlet fever include:

Chills
Fever
Fatigue
Headache
Muscle aches
Sore throat and a swollen tongue
Red color in the creases of your armpit and groin
Stomach pain
Vomiting

Scarlet fever is contagious. Once you're infected, it only takes one or two days to start developing symptoms.

Causes of scarlet fever

As mentioned above, bacteria called group A Streptococcus, or group A strep, cause scarlet fever. The bacteria sometimes make a poison, known as an endotoxin, that gives you a scarlet-colored rash.

Group A strep live in your nose and throat and are easily passed to other people. Not everyone who is infected has symptoms. The bacteria is spread through small respiratory drops that are released into the air when you cough or sneeze.

Infection occurs when you:

Inhale the droplets
Touch a surface with droplets on it, then touch your mouth or nose
Share drinks, food, or utensils with someone who is sick
Touch sores on the skin

In rare cases, scarlet fever or strep is spread through food that isn't properly handled.

When to see the doctor for scarlet fever

If you or someone in your family suddenly develops a fever, sore throat, swollen glands, or a red rash, call your doctor. This is especially important if you know someone who recently had strep. These infections are easily spread at school, in daycare, or in the office.

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Diagnosing scarlet fever

There are many viruses and bacterial strains that lead to a sore throat and rash. To determine whether your illness is actually scarlet fever, you'll need a rapid strep test or throat culture.

Your doctor will likely start with a rapid strep test, which involves swabbing your throat, then testing it. The results will show if bacteria from group A strep is causing your illness. If the result is positive, you'll be prescribed antibiotics.

If test results come back negative but your doctor still suspects you have scarlet fever, they will take a throat culture swab and send it to a lab for further analysis. The throat culture takes longer, but once the bacteria are given a chance to grow and multiply, a culture can identify infections the rapid strep test might miss.

Doctors will often use both a rapid strep test and throat culture on children and teens, because it's possible to develop rheumatic fever, an autoimmune disease, from an untreated infection.

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Treatments for scarlet fever

Scarlet fever is treated with antibiotics. If you aren't allergic to penicillin, you'll likely be prescribed penicillin or amoxicillin. People who have a penicillin allergy will take a different course of antibiotics.

While taking antibiotics, you can alleviate symptoms by:

Taking an over-the-counter (OTC) painkiller, like acetaminophen or ibuprofen
Gargling with warm salt water to soothe a sore throat
Using a cool-mist humidifier to make breathing easier
Consuming more liquids, including warm soups and cold drinks, to help you swallow solid foods

Long-term effects of scarlet fever

Scarlet fever is no longer contagious after you've been on antibiotics for 24 hours. The rash generally fades within a week, but can linger for up to two weeks in some patients.

While rare, scarlet fever does have some complications if the strep bacteria spreads to other parts of the body. Complications include:

Swollen lymph nodes in the neck
Sinus, skin, and ear infections
Pockets of pus, or abscesses, around your tonsils
Rheumatic fever, which affects your heart
Pneumonia, a lung infection
Arthritis, or joint inflammation
Post-streptococcal glomerulonephritis, a kidney disease

Taking antibiotics can prevent most of these health problems.