Viral exanthem rashes are skin rashes that occur due to virus infections. The rash is often accompanied by fever and other systemic symptoms. It starts from one part of the body and gradually spreads to other areas.¹ It is important to differentiate harmless skin rashes from more serious and life-threatening ones. Diagnosis of different types of exanthem rashes depends on the symptoms present. Treatment mainly aims to provide relief from the symptoms. 

What is a viral exanthem rash?

A viral exanthem rash is a skin rash that is caused by the infection of a virus. It presents with skin eruptions that gradually spread throughout the body. The rash is associated with other symptoms like fever, fatigue, sore throat, and body pain.²

Viral exanthem rashes commonly occur during childhood. They are diagnosed based on the cause of the infection, the appearance of the rash, the time course of the eruptions, and their distribution throughout the body.³ Most of the viral exanthems resolve on their own with treatment of symptoms like fever and itching. Once the infection has spread, antiviral therapy is required to treat the disease.²

Causes of viral exanthem rash

Viral exanthems are caused by infection of certain types of viruses. This can be by direct contact with an infected person or indirect contact with a contaminated object. The virus spreads through droplets or skin contact.² Rashes are caused by the virus itself or by the toxins produced by the virus. They may also occur as a reaction of the body's immune system to the virus.¹ 

Viruses responsible for exanthem rashes include:^{1 4} 

• Varicella zoster virus - chickenpox
• Morbillivirus - measles
• Rubella virus - rubella
• Human herpesvirus 6 - roseola
• Parvovirus B19 - fifth disease
• Coxsackievirus A16 - hand, foot, and mouth disease
• Coronavirus - COVID19
• Human immunodeficiency virus - AIDS
• Hepatitis virus - Hepatitis

Symptoms

Viral exanthem rashes are characterized by spots and blotches on the skin. The rashes begin on a particular part of the body, mostly the face and trunk, from where they spread to other parts.¹ Apart from rashes, exanthems also present with systemic symptoms which include:²,⁵

1. Fever 
2. Cough 
3. Sore throat 
4. Abdominal pain 
5. Fatigue 
6. Swollen lymph nodes
7. Conjunctivitis 
8. Headache 
9. Nausea 
10. Vomiting
11. Loss of appetite
12. Irritability

Types of viral exanthems

The common viral exanthems are chickenpox, measles, rubella, roseola, and fifth disease.⁶ 

Chickenpox

The Centers for Disease Control(CDC) recommends that all children should be vaccinated between 12 to 18 months of age for chickenpox.⁶ Chickenpox is caused by the varicella-zoster virus. It is characterized by blisters on the trunk and limbs and is highly contagious.⁴

Measles

Measles is caused by paramyxovirus. It is characterized by fever, cough, conjunctivitis, and stuffy nose. Grey-white spots(Koplik spots) seen on oral mucosa are characteristic of measles. Red rashes begin to appear from the head and spread to the trunk and extremities. These fade from the fifth day onwards.⁷

Rubella

Pink rashes appear on the face and spread to the trunk and limbs. Tender lymph nodes and arthritis are also characteristic of rubella. Rubella infection during pregnancy causes congenital rubella syndrome in children. Hence, it is important for women to get timely vaccination against the disease.⁷

Roseola

Roseola occurs in children less than 3 years of age. It is caused by human herpesvirus 6. Rashes appear on the trunk and arms along with eyelid swelling, high fever, abdominal pain, and fatigue.⁴

Fifth disease

The fifth disease is also called erythema infectiosum. It is caused by human parvovirus B19. It commonly occurs in children. Symptoms are mild and include low fever, headache, itching, runny nose, and sore throat. The bright red rash begins on the cheeks and spreads to the trunk and extremities.⁶

Diagnosis of viral exanthems

Viral exanthem rashes are diagnosed based on morphology, distribution, location, and time course of the eruptions.⁸ The systemic symptoms along with the distinct pattern of rashes allow to differentiate between the viral infections.⁹ Accurate diagnosis of the rash is important for the correct management approach to be taken. Diagnosis involves the following elements:

• Medical history

It is important to take the history of the patient to determine the time course of the rashes and the source of the infection.

• Clinical examination: 

The colour, size, distribution, location, elevation, palpation, and content of the skin lesion helps to diagnose the viral exanthem.⁵ 

• Laboratory examination:¹⁰
  • Swab test - A swab from the skin or oral mucosa can be used to detect the virus responsible for the rash.
  • Cell culture - It identifies herpes simplex virus, varicella-zoster virus, and others.
  • Blood tests - Complete blood count: Viral infection raises or reduces the blood count. 

C-reactive protein: Level is elevated.

Serology: Tests the immune response to the virus. 

4. Polymerase Chain Reaction(PCR): PCR tests the DNA to identify the virus responsible for the disease
5. Enzyme-Linked Immunosorbent Assay(ELISA): It detects the antigen or antibody associated with the viral infection. HIV, hepatitis virus, and varicella zoster viruses are commonly detected by ELISA
6. Skin biopsy
7. Electron microscopy detects rare viral infections
8. Genotyping: It identifies the causative virus from DNA samples¹¹ 
9. Resistance testing: Helps to determine which antiviral drug can and cannot be used, especially in immunosuppressed patients

Prevention

Timely vaccinations can prevent the occurrence of viral exanthems to an extent. Avoid close contact with infected persons. Maintaining proper hygiene and avoiding close contact with people can prevent the spread of the disease.¹

Treatment

Treatment of viral exanthems depends on the cause. It mainly aims to provide relief from the symptoms of the exanthem rashes. Most viral infections are relieved on their own with the treatment of symptoms like fever, pain, and itching from the rashes.² In severe infections, antiviral medications are necessary to treat the disease.

Symptomatic treatment

Antipyretics and painkillers are used for symptomatic relief from viral infections. Over-the-counter drugs like paracetamol and NSAIDs are used to relieve fever, pain, and discomfort.¹ Itching from the rashes is treated by topical corticosteroids, antihistamines, and moisturizing emollients.^{2 8} 

Antiviral therapy

Severe cases of viral exanthems are treated using antiviral medications. Antiviral therapy reduces the duration of the disease and provides relief from the associated pain. The medications include acyclovir and valacyclovir used in the treatment of varicella zoster and herpes simplex virus infections.¹²

Home remedies

Adequate fluid intake and rest are essential to hydrate the body and prevent any complications. Calamine lotion can be used to relieve itching from the rashes along with taking cool baths.⁶ Take care not to scratch the skin blisters to prevent scars and further infections. Proper isolation and hygiene are needed to prevent the spread of the virus.¹

When to seek medical attention?

Consult a doctor immediately if you notice any swellings or rashes on skin along with itching and high fever. These symptoms are suggestive of skin infection and should not be ignored.  

FAQs

What are the complications of viral exanthem rashes?

If left untreated, viral exanthems can lead to further skin infections and scarring.¹ Secondary bacterial infections, pneumonia, and encephalitis are some other complications usually seen in immunocompromised patients. Seizures can occur in children with roseola left untreated.⁶

What are the home remedies for viral exanthems?

Rest and fluid intake are necessary for hydration and prevention of infections. Taking cool baths and using moisturizers on the rashes help to relieve itching. Over-the-counter painkillers and antipyretics can be used for symptoms like pain, discomfort, and fever.

How long does the rash last?

The rashes last from a few days to one or two weeks depending on the type of infection. Consult a doctor to know the time course of the disease and proper treatment measures.

Summary

Viral exanthem rashes are skin eruptions that occur due to virus infections. They present as rashes, blotches or blisters on the skin along with pain, fever, and other systemic symptoms. Measles, chickenpox, and scarlet fever are some examples of viral exanthems. Diagnosis involves clinical examinations and laboratory tests. Blood and swab tests are performed to identify the virus causing the infection. Treatment mainly aims to relieve the symptoms. Severe infections are treated by antiviral therapy. Proper vaccinations can prevent the occurrence of viral exanthems to an extent. It is important to consult a doctor immediately and get treated to prevent any further complications.