Papular urticaria is a common skin disorder caused by a hypersensitivity reaction to insect bites like mosquitoes, fleas, and bedbugs. Individual papules form around the site of the bite and have a central punctum. The pathogenesis involves a Type I hypersensitivity reaction where an antigen from the insect bite disseminates in the bloodstream and sensitizes the patient. Lesions are itchy papules and papulovesicles that appear symmetrically on exposed areas of the body and heal with hyperpigmentation. Management focuses on relieving itching with topical steroids or antihistamines, with short term oral corticosteroids for severe cases.

1. Papular Urticaria
Prof. Dr. Essamelden Mohamed Mohamed
Professor of Dermatology, Al-Azhar university
dessam73@azhar.edu.eg

2.  Papular urticaria is a common disorder manifested by chronic
or recurrent papules caused by a hypersensitivity reaction to
the bites of mosquitoes, fleas, bedbugs, and other insects.
 Individual papules may surround a wheal and display a
central punctum.

3. Etiology
A hypersensitivity or id reaction to
bites from insects, such as
mosquitoes, gnats,
fleas, mites, bedbugs, caterpillars, an
d moths.
This Photo by Unknown author is licensed under CC BY.

4. Pathogenesis
Type I hypersensitivity reaction
Caused by a hematogenous
disseminated antigen deposited by
an arthropod
bite sensitive patient .
The causative antigen is unknown

5. Pathogenesis
The presence of immunoglobulin and
complement deposits in the skin of
some patients with papular urticaria
suggests that the lesions may be due
to a cutaneous vasculitis.
The deposits were most frequently
seen in lesions within 24 hours of their
development.
This Photo by Unknown author is licensed under CC BY-SA-NC.

6. Histopathology
Mild subepidermal edema.
Extravasation of erythrocytes.
interstitial eosinophils, and
exocytosis of lymphocytes.
This Photo by Unknown author is licensed under CC BY-SA.

7. Clinical
Evaluation
Itchy symmetrically distributed
papules and papulovesicles occur on
any body part.
Common on exposed areas ,
particularly the extensor surfaces of
the extremities.
A central hemorrhagic punctum.
Heal by hyperigmentation.

8. Differential Diagnosis
Dermatitis Herpetiformis
Id Reaction
Impetigo
Insect Bites
Pityriasis Lichenoides

9. Management
Symptomatic in most cases.
Mild topical steroids and systemic antihistamines for
relief itching
Short-term systemic corticosteroids for sever cases.
Topical or systemic antibiotics for 2ry bacterial infection.
Insect repellents .

11. This Photo by Unknown author is licensed under CC BY-SA-NC.