Infectious diseases: Scarlet fever

Diagnosis and management of scarlet fever.

Strawberry tongue is often seen in patients with scarlet fever (Picture: Dr Nigel Stollery)

Scarlet fever, previously known as scarlatina, consists of a syndrome characterised by a fever, bright red exanthem and an exudative pharyngitis. It is caused by the toxin-producing group A beta-haemolytic streptococci (GABHS).

Public Health England (PHE) recorded 14,387 scarlet fever notifications between September 2014 and the end of June 2015.1 Notifications peaked in week 13 of 2015, with more than 1,200 cases notified.


The condition most commonly affects the five to 15 years age group and is most common in the winter and spring. It is rare in the under-twos, owing to the presence of maternal anti-exotoxin antibodies.

The most common form of transmission is by respiratory droplets in close contact, but the ability of the organism to survive variations in temperature and humidity means spread via fomites can occur.

Hand washing and covering the mouth when coughing and sneezing should be encouraged to prevent the spread of the condition where outbreaks are reported.

Rarely, transmission can occur via food. This was the reported cause of an outbreak in China.2

Males and females are equally affected, with no ethnic variations. The incubation period varies from 12 hours to seven days.

Onset is usually rapid, with fever, sore throat, vomiting, headache, abdominal pain, myalgia and malaise. This is followed 12-48 hours later by a rash, which usually starts on the neck then extends to the trunk and extremities.

The rash occurs as a result of the local production of inflammatory mediators and alteration of the cutaneous cytokine milieu, resulting in dilation of blood vessels and the characteristic scarlet appearance of the rash.3

The rash is a fine erythematous punctate eruption, which blanches with pressure. This is followed by dry rough skin, with the feel of sandpaper. Seven to 10 days later, desquamation will occur of all affected areas, which may last on the palms for up to a month.

The fever peaks on the second day and will usually settle in five to seven days.

The tongue is usually heavily coated, with the papillae visible through the coating. This coating sloughs off, leaving a red, shiny, so-called strawberry tongue, with prominent papillae. The pharynx and tonsils will have a typical thick exudate, similar to that seen in bacterial tonsillitis or glandular fever.

Differential diagnosis

  • Fifth disease
  • Rubella
  • Rubeola
  • Epstein-Barr virus infection
  • Tonsillitis
  • Paediatric erythema toxicum
  • Exfoliative dermatitis
  • Rat bite fever
  • Toxic shock syndrome
  • Secondary syphilis
  • Kawasaki disease
  • Acute lupus erythematosus
  • Drug eruptions
  • Pityriasis rosea


  • Peritonsillar abscess
  • Sinusitis
  • Bronchopneumonia
  • Meningitis
  • Hepatitis
  • Septicaemia
  • Rheumatic fever
  • Glomerulonephritis
  • Septic shock, multi-organ failure


Investigations are not always required and the diagnosis can usually be made clinically, based on the rash and symptoms. Outbreaks of the condition usually occur, which can also help with the diagnosis.

A throat swab and culture and antistreptolysin O titres can be helpful if the diagnosis is in doubt.

The carriage rate of GABHS in healthy individuals is 10-15%, so a positive swab is not proof of the disease.


The treatment of choice is 10 days of penicillin VK or a cephalosporin. In those who have a documented allergy to penicillin, erythromycin should be used as an alternative.

Children can return to school 24 hours after starting the antibiotics if they are systemically well enough.

Patient education is very important – symptoms will often settle over a few days, but it is essential to complete the course of antibiotics, to prevent the development of complications (see box 1).

Symptomatic treatment, such as paracetomol, can help with the fever, and fluids should be maintained to prevent dehydration.

For the skin desquamation, emollients should be advised, with antihistamines for any pruritus. Topical steroids are of little help.


The prognosis is usually excellent, with most patients recovering after four to five days and the rash clearing over four to five weeks. This was not the case in the days before antibiotics, when mortality was as high as 15-20% of those affected.

At present, there is no vaccine against this condition, but it is thought that by 10 years of age, 80% of the population will have developed lifelong immunity to the causative organism.

  • Dr Stollery is a GPSI in dermatology in Kibworth, Leicestershire

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  1. PHE. July 2015. Health Protection Report, vol 9, no 23. Group A streptococcal infections, 6th update on seasonal activity, 2014/15
  2. Yang SG, Dong HJ, Li FR et al. J Infect 2007; 55(5): 419-24
  3. Cunningham MW. Clin Microbiol Rev 2000; 13(3): 470-511

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