Understanding Urticaria Multiforme: Beyond the Typical Hives

March 8, 2024

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Urticaria multiforme (UM) is a unique type of skin reaction that causes a distinctive rash made up of round or oval-shaped hives with reddened centers, making them look “target-like”. These hives, also known as wheals or lesions, are often accompanied by symptoms like fever, itching, swelling, and facial flushing in infants and young children.

While UM may initially appear concerning to parents, it is important to understand that this polymorphic dermatological manifestation is usually temporary and often resolves on its own. However, an accurate diagnosis from a doctor is critical to rule out other potentially dangerous conditions.

What is urticaria multiforme (UM)?

Urticaria multiforme (UM), also known as polymorphic urticaria, is a form of acute urticaria characterized by the sudden onset of distinctive target-shaped hives ranging in size from a few millimeters to several centimeters. These multiform lesions have a central wheal surrounded by a ring of erythema (redness) and peripheral pallor, giving them a “bull’s eye” appearance.

Along with the variable skin rash, UM is also frequently associated with mild constitutional symptoms like low-grade fever, malaise, and joint pain. Itching of the skin lesions is common as well. Facial swelling, especially of the lips and around the eyes, can also sometimes occur.


Distinguishing Urticaria Multiforme

Differentiating UM from Other Conditions

While the polymorphic manifestations of UM may be alarming at first glance, it is important to understand that this is a distinct condition that must be differentiated from other similar-appearing skin reactions.

Urticaria multiforme (UM) can be mistaken for erythema multiforme, another condition marked by targetoid lesions. However, erythema multiforme lacks the significant itching and typical urticarial nature of UM rashes.

UM also needs to be distinguished from serum sickness, an immune reaction to certain medications or antiserum that causes hives and swelling. Unlike serum sickness, UM usually occurs without any recent exposure to new drugs or biological agents.

Furthermore, UM shares some superficial similarities with Kawasaki disease, a serious childhood illness affecting blood vessels. However, Kawasaki disease has additional symptoms not seen in UM, like conjunctival injection and oral mucosal changes.

For these reasons, consultation with a pediatrician or dermatologist is very important to confirm an accurate diagnosis of urticaria multiforme and to rule out other possibly dangerous conditions. Misdiagnosis and self-treatment should be avoided.

Symptoms of Urticaria Multiforme

The distinctive lesions of urticaria multiforme (UM) appear rapidly, sometimes within a matter of hours. The individual wheals last for about 24-48 hours before fading, but new hives may continually form for several days or weeks.

In addition to the unique targetoid hives, UM is also often accompanied by:

  • Fever – Typically low-grade fevers under 102°F.
  • Facial swelling – Particularly of the lips and around the eyes.
  • Itching – Significant itching sensation on the skin lesions and occasionally elsewhere.
  • Malaise – Generally feeling unwell.
  • Joint pain – Mild achiness in the joints.

While the variety of symptoms may be initially frightening, parents can find reassurance in the benign and temporary nature of UM.


Understanding the Causes of UM

Common Triggers in Children

The exact causes of urticaria multiforme are not always identified, but the condition is frequently associated with viral illnesses in affected children. Cases often follow infections like:

  • Influenza
  • Hand, foot and mouth disease
  • Herpangina
  • Viral pharyngitis

The rash usually appears early in the course of these viral illnesses or during recovery. However, a direct causal relationship has not been clearly established, so UM is generally considered a secondary condition rather than a direct result of the viral infection itself.

Less commonly, medications, vaccinations, or infections beyond viruses have also been linked to UM. The underlying immune or inflammatory response likely plays a key role in the polymorphic eruptions.

Who Gets Urticaria Multiforme?

Urticaria multiforme (UM) most commonly affects infants and young children under 10 years old, with peak incidence around 1-2 years old. It is more frequently seen in boys than girls.

Recurrence is common, with about one third of patients experiencing at least one additional episode of UM later in childhood. The condition rarely occurs in adulthood.


Diagnosis and Treatment of UM

Consulting a Doctor

Due to the varied manifestations and risk of misdiagnosis, it is very important to seek evaluation from a healthcare professional if urticaria multiforme is suspected. In some cases, laboratory tests or even skin biopsy may be recommended to rule out other conditions.

“Making an accurate diagnosis is crucial before starting any treatment when unusual rashes appear in children,” says Dr. Linda Gomez, pediatric dermatologist“While urticaria multiforme often follows a benign course, we need to exclude potentially dangerous mimics like serum sickness or cutaneous vasculitis through proper diagnostic methods.”

With an accurate diagnosis from a doctor, parents can find reassurance that UM is a temporary condition that will resolve on its own.

Treatment Options

In the majority of urticaria multiforme (UM) cases, the condition is self-limited and resolves within several weeks without any specific treatment.

However, antihistamines may provide relief from severe itching. Oral diphenhydramine (Benadryl) or non-sedating second generation antihistamines like cetirizine (Zyrtec) or loratadine (Claritin) may be recommended under a doctor’s supervision.

If UM occurs frequently or persists longer than 6-8 weeks, further investigation into underlying causes may be warranted. Beyond antihistamines, inducing tolerance through specialist methods could be explored for severe refractory cases under medical guidance.

Reassurance and Support for Parents

A Self-Resolving Condition

The transient and non-threatening nature of urticaria multiforme (UM) offers reassurance to worried parents. Most cases follow a short-lived course without complications, generally resolving completely in days to weeks.

Recurrences, while inconvenient, are also limited and unlikely to cause any permanent issues or long term health consequences. With this understanding, parents can find comfort in calmly waiting out this frustrating but ultimately harmless process.

“It was certainly unsettling when my 18-month-old’s face and body were suddenly covered in red welts and hives,” recounts mom Janelle Roberts. “However, our pediatrician explained that urticaria multiforme is common in little ones and would clear up on its own. Sure enough, the rash began fading after several days and was gone completely within two weeks.”

Managing Symptoms at Home

While urticaria multiforme (UM) runs its course, keeping the child comfortable is key. Loose, lightweight, and non-irritating clothing can help avoid worsening itch. Lukewarm baths for 20 minutes can temporarily soothe inflamed skin. Oral antihistamines may also provide itch relief if recommended by your doctor.

However, be sure to avoid excessive warming measures like hot baths, heating pads, or vigorous rubbing which can worsen symptoms. Chilling the skin with ice packs is not advised either. Overall, gentle care helping the skin heal on its own works best for UM.


  • Urticaria multiforme is a unique type of skin reaction in children causing target-shaped hives, fever, and itching.
  • It often resolves on its own, but consulting a doctor is crucial to rule out other conditions.
  • Parents can find reassurance knowing UM is temporary and manageable with proper care.


What does urticaria multiforme look like?

Urticaria multiforme causes a distinctive rash made up of round or oval-shaped hives (wheals) with pale rings around dark red centers, creating target-like lesions.

Is urticaria multiforme contagious?

Urticaria multiforme itself is not contagious. However, some underlying viral infections that may trigger UM can be contagious.

How long does urticaria multiforme last?

Most cases of urticaria multiforme resolve on their own within 1-3 weeks. Severe cases may persist slightly longer.

What can I do at home for my child with urticaria multiforme?

Loose lightweight clothing, lukewarm baths, and oral antihistamines (under medical supervision) may help relieve discomfort. Avoid irritating or heating the skin.

Can adults get urticaria multiforme?

While rare, urticaria multiforme can occasionally affect adults as well. Regardless of age, seeing a doctor for accurate diagnosis is recommended.

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