Strophulus: symptoms of itchy bumps caused by insect bites

Strophulus, sometimes called ‘papular urticaria’, is an acute eruption of red, very itchy bumps on the skin caused by a hypersensitivity reaction to insect bites, such as mosquitoes, fleas and bedbugs. Such a bump closely resembles the consequences of the insect bite itself. Treatment often consists of controlling the symptoms with corticosteroid cream. The allergic reaction can be suppressed with oral antihistamines.

  • What is strophulus?
  • Synonyms
  • Cause strophulus
  • Symptoms of strophulus
  • Bumps
  • Blisters and itching
  • Examination and diagnosis
  • History and physical examination
  • Differential diagnosis
  • Treatment strophulus
  • Prognosis

 

What is strophulus?

Strophulus is a common and often annoying condition that manifests itself as red papules (bumps) on the skin caused by a hypersensitivity reaction to insect bites. This includes the bites of mosquitoes, fleas, bed bugs, and other insects. This (delayed) hypersensitivity reaction is mainly found in children between 2 and 8 years old, especially in the summer and autumn.

Synonyms

Strophulus is also known by the following names:

  • strophulus pruriginosus;
  • strophulus infantum;
  • prurigo infantum; and
  • lichen urticatus.

 

Cause strophulus

Strophulus is a hypersensitivity reaction to insect bites from arthropods, such as mosquitoes, fleas, mites and bedbugs (formerly called ‘bedbugs’). This concerns a hypersensitivity to certain protein components present in the insect’s saliva. In children with building hypersensitivity, desensitization eventually occurs, causing strophulus to disappear.

Symptoms of strophulus

Bumps

Strophulus is characterized by grouped symmetrically distributed pruritic urticarial papules, often surrounded by a red border. These bumps are mainly located on the extremities of the extremities and to a lesser extent on the face, neck, trunk, thighs and buttocks. It does not usually occur in the genital and perianal regions and the armpits.

Blisters and itching

The bumps are 3-10 mm in diameter. Sometimes (fluid) blisters or blisters also develop, which is called ‘strophulus bullosa’. The spots can itch intensely, causing scratching effects. Scratching can lead to erosions and ulcers. The lesions last between two and twelve days. After the bumps have gone away, redness or pigmentation may remain. After a new bite, older spots can become more active again. The condition is chronic or recurrent. The bumps can return for years if the child is stung again.

Examination and diagnosis

History and physical examination

The GP often makes the diagnosis by eye. He will also ask questions about your complaints and when it started; whether you were recently bitten by an insect. He will look at the bumps and often that is enough. If necessary, additional research can be done in the form of a skin biopsy.

Hives on the back / Source: DLdoubleE, Wikimedia Commons (Public domain)

Differential diagnosis

The following conditions can give a similar picture:

  • Early chickenpox;
  • common urticaria (hives, hives);
  • Gianotti-Crosti syndrome (GCS);
  • Scabies or scabies;
  • Pityriasis lichenoides.

 

Treatment strophulus

In most cases, the treatment of strophulus is symptomatic, which means: aimed at the complaints. Application of a mild corticosteroid cream (hormone ointment) to relieve itching and oral antihistamines to suppress the allergic reaction. Furthermore, it is important to remove any arthropod insects from the child’s environment, especially in pets.

Prognosis

The prognosis is good. After treatment, the bumps disappear quite quickly. You are often free of complaints within a few days. Just make sure you stay away from insects.

read more

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