Pityriasis means “scaly,” and rosea means “pink,” even if the rash can be red, gray-brown, or purple depending on the skin type. Pityriasis rosea is a common, acute, and self-limiting skin condition primarily of children, adolescents, and young adults. It is clinically defined as the sudden eruption of a characteristic rash, beginning with a solitary, large lesion on the chest, abdomen, or back, called the “herald patch.” Within days to weeks of the herald patch, multiple smaller, oval, scaly lesions typically develop on the trunk and proximal limbs. The secondary lesions typically align with natural lines of skin in a pattern sometimes described as “a Christmas tree” effect. 

Although the exact cause of pityriasis rosea is unknown, it is believed to be primarily viral, with reactivation of human herpesvirus types 6 and 7 most commonly implicated. The condition typically affects individuals between the ages of 10 and 35 but can occur at any age, including during pregnancy. It is more common in spring and fall, though it can appear year-round. Once resolved, the rash usually does not return.

Some patients describe mild flu-like symptoms, including malaise, headache, sore throat and low-grade fever, in the weeks preceding the rash, which provides a rationale for the existence of a viral infection. Clinically, the herald patch is often misdiagnosed as ringworm utilizing the features of a round or oval plaque with a scaly edge and central clearing. The additional lesions that develop along the trunk and upper proximal extremities appear similar and each grows symmetrically. The rash is pink or salmon-colored in lighter skin tones, but grey, brown and purplish on darker skin tones. 

The rash may cause mild to moderate pruritis, but pityriasis rosea is a benign self-limited condition. It typically resolves on its own within 6-10 weeks and does not cause scarring. Since pityriasis rosea is not infectious or harmful, treatment is generally limited to symptomatic relief.

The specific cause of pityriasis rosea is unclear, but there is considerable evidence to suggest that pityriasis rosea is of viral origin, particularly human herpesvirus 6 and 7 (HHV6 and HHV7); these same viruses cause roseola infantum in infants. The reactivation of these viruses may trigger pityriasis rosea in some individuals. 

Pityriasis rosea is not contagious and not spread by direct contact or respiratory droplets. Most presentations occur without any obvious cause, but some common triggers are: 

• Stress or stressful events or short-term immune suppression.
• Autoimmune response to the viral antigens.
• Drug reactions, or pityriasis rosea-like rashes. 

It has been noted that pityriasis rosea may follow a few vaccinations, but these are rare: 

• BCG
• H1N1
• Diphtheria
• Smallpox
• Hepatitis B
• Pneumococcal
• COVID-19 Vaccinations

These are rare, but generally mild cases.

Although pityriasis rosea is likely viral (most probably human herpesvirus type 6 and type 7, HHV-6 and HHV-7) in nature, pityriasis rosea is not contagious, and thus spreads by skin contact, airborne droplets, or surfaces of other infected individuals. People’s first thoughts about pityriasis rosea is usually: If I don’t know anyone with a viral illness, how did I develop pityriasis rosea?  

Most people with viral HHV-6 or HHV-7 are carriers in a latent (inactive) state; the viruses may reactivate if stressed over a prolonged period, sick with symptoms, or have changes in one’s immune system, which may lead to the rash. 

Key Points:

• You don’t “catch” pityriasis rosea from another person.
• Most people with pityriasis rosea cannot identify their exposure or risk factors.
• It usually occurs spontaneously, without an apparent cause.
• Cases have been reported to occur seasonally in spring and fall (when common viral illnesses occur) suggesting a possible correlation, especially among adults.  
• If either of your parents, have pityriasis rosea, your risk may slightly increase.  

Some medications have been associated to a pityriasis rosea-type eruption which include (a partial list):  

• Terbinafine  
• Isotretinoin  
• Omeprazole  
• Gold salts  
• Arsenic  
• Barbiturates  

In summary, pityriasis rosea usually occurs without warning and likely reflects viral reactivation or an immune response to viral illness, not transmissibility.

Pityriasis rosea typically follows an identifiable and self-resolving course that takes place over a few weeks. Although the rash is the defining feature of the condition, mild systemic symptoms may begin a few days in advance.

1. Prodromal Phase (Preceding the Rash): In the days before the rash, some patients experience flu-like symptoms that are usually mild and transient. These can include:
   • Fatigue
   • Headache
   • Mild fever
   • Sore throat
   • Loss of appetite
   • Extra lymph nodes
   • These mild symptoms occur in less than half of the patients and generally resolve before the skin eruption starts.
2. Herald Patch (Mother Patch): The first skin sign is usually a single, large patch called a herald patch or mother patch. It:
   • Is 2–10 cm in diameter
   • Is on the chest, abdomen, or back
   • Has a central clearing with an elevated, scaly border
   • It might look similar to ringworm or eczema
   • For light-skinned individuals, it appears to be pink or red. For darker-skinned individuals, it varies and can be violet, gray, brown, or dusky. The herald patch often goes unnoticed or mistaken for another skin condition.
3. Secondary Rash (Daughter Patches): A few days to two weeks following the development of the herald patch, multiple smaller lesions arise. These daughter patches:
   • Are oval-shaped and scaly
   • Align according to Langer’s lines (natural lines of skin cleavage), forming a “Christmas tree” pattern on the back
   • Generally, are on the trunk, upper arms and thighs
   • Typically spare the face, especially among adults
   • In about 50% of cases, the rash is itchy, ranging from mild to moderate. Symptoms may also be exacerbated by heat; with sweat, and tight clothing.
4. Changes in Color and Resolution: The lesions may have an initial pink or salmon hue, followed by a darkening as they evolve. Eventually, they begin to fade, sometimes leaving the patient with some transient dyschromia or scaling, especially with darker complexions. In most cases, the rash resolves in about 6 to 8 weeks, with some lasting as long as 12 weeks.

Pityriasis rosea is almost always diagnosed clinically based on the rash appearance and distribution. No non-invasive tests can reliably assess this diagnosis. A healthcare provider or clinician should be able to diagnose pityriasis rosea during a physical exam especially in the presence of herald patch and the classic “Christmas tree” pattern.

Diagnostic features:

• Herald patch as a first distinctive rash
• Symmetrical oval lesions on the trunk
• Rash conforms to tension lines of the skin (Langer’s lines)
• Fine scaling with central clearing
• Additional tests (if necessary)

If the rash is a less typical presentation, ancillary tests may rule out similar conditions:

• Tinea corporis (ringworm) – KOH prep or fungal culture can rule out
• Secondary syphilis – requires blood tests (RPR and/or VDRL)
• Psoriasis or eczema
• Drug induced eruptions

Skin Biopsy: If the diagnosis is uncertain, skin biopsy may be performed. It will help rule out other diagnoses; however, histopathologic findings in pityriasis rosea are generally non-specific.

Blood Tests: While not routine, blood tests may be used to check for infections or exclude other causes in unusual presentations.

In most cases, a clinical exam is sufficient, and no further testing is needed unless symptoms are atypical or persistent.

Pityriasis rosea is a self-limiting skin condition that usually resolves on its own within 4 to 10 weeks. Most of the time treatment is not required but some patients may need relief of symptoms, in particular those that are itchy or uncomfortable. 

General Management:

• Reassurance: Inform the patient that this condition is benign, self-limiting, and temporary, may reduce anxiety for patients. 
• Observation: Although most rashes spontaneously resolve in the first 6 to 8 weeks, while the average duration is 6 weeks, you can reassure your patient that there are no complications.

Itch Relief: For patients who are experiencing itchiness, the following may help:

• Oral antihistamines (e.g., diphenhydramine, loratadine).
• Topical corticosteroids (low- to medium-potency) to diminish inflammation.
• Calamine lotion or colloidal oatmeal baths. 
• Moisturizers (preferably fragrance-free) to prevent dry skin and irritation.

Phototherapy: For more persistent or symptomatic cases, you could consider narrowband UVB phototherapy or controlled natural sunlight exposure that can:

• Reduce inflammation.
• Facilitate the resolution of rash.

Caution: Avoid prolonged sun exposure to prevent sunburn, which can worsen the condition.

Antiviral Medications: Acyclovir, an antiviral medication, may shorten the duration in select cases, when started sooner. However, it is not generally recommended for routine use, especially considering the limited and mixed evidence 

Avoidance of Irritants: To avoid further aggravation of the rash, be sure to:

• Use soothing and fragrance-free topical or skin care products.
• Avoid hot showers or baths.
• Wear loose-fitting, breathable clothing.

Pityriasis rosea is a benign, self-limiting skin condition mostly affecting adolescents and young adults. It often starts with a single herald patch and is then followed by an asymmetrical, scaly rash that travels in a line along the natural skin tension lines—often creating a “Christmas tree” pattern on the back.

The cause of pityriasis rosea is suspected to be of viral origin, possibly human herpesvirus types 6 and 7 (HHV-6 and HHV-7), although there is not enough evidence to prove this theory. Pityriasis rosea is not contagious, and self-limiting and is likely to resolve within weeks to months without medical treatment.

The management of pityriasis rosea is aimed towards alleviating symptoms, particularly those with itching. Supportive treatments for pityriasis rosea include antihistamines (oral); topical corticosteroids, moisturizer, and soothing skin care. Patient education and reassurance play an important role in decreasing anxiety and promoting recovery.

Most people recover completely without complications or recurrence from pityriasis rosea; on occasion the rash may persist longer or recur, but rarely. If the rash seems atypical and/or it is unresponsive to standard management, a clinical re-evaluation is recommended to exclude other skin disease.

With a good understanding of the condition, supportive care, and reassurance, pityriasis rosea can be managed effectively to allow aspects of daily living to proceed largely uninterrupted. It is important to remain attentive to any new or changing skin symptoms, and the health care provider should be contacted with promptness.

Chuh, A. A., & Zawar, V. (2022). Pityriasis rosea: An update. Indian Journal of Dermatology, Venereology, and Leprology, 88(1), 11–20.

American Academy of Dermatology. (2021). Pityriasis rosea

Drago, F., Ciccarese, G., Parodi, A., Broccolo, F., & Rebora, A. (2018). Pityriasis rosea and pityriasis rosea-like eruptions: How to distinguish them? JAAD Case Reports, 4(8), 723–724.

Watanabe, T. (2018). Pityriasis rosea: Etiology and management. American Journal of Clinical Dermatology, 19(3), 357–372. 

Broccolo, F., Drago, F., Careddu, A. M., Foglieni, C., Turbino, L., Cocuzza, C. E., & Toniolo, A. (2015). Additional evidence that pityriasis rosea is associated with reactivation of human herpesvirus-6 and -7. Journal of Investigative Dermatology, 135(2), 729–730.