Allergic contact dermatitis

Contact allergic dermatitis occurs in patients in response to a facultative irritant (allergen) to which there is increased sensitivity. Allergic dermatitis is based on a delayed-type allergic reaction. Medicinal and chemical substances often act as allergens. They (haptens), combining with epidermal proteins, acquire the properties of a complete antigen. Allergens bind to mast cells (macrophages) of the epidermis, which transmit information about the antigen to T-lymphocytes. In response to this, T-lymphocytes proliferate with the formation of a population of cells specific to this antigen. Upon repeated contact with the allergen, sensitized lymphocytes accumulate in the site of action of the allergen. Lymphocytes secrete various interleukins, which attract mast cells and polymorphonuclear leukocytes to the site. As a result of degranulation of the latter, biologically active substances (histamine, bradykinin, etc.) are released, which contribute to the formation of an acute inflammatory process in the skin.

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Histopathology

Intercellular edema in the epidermis, hypertrophy and hyperplasia of the endothelium and perithelium of the vessels, and narrowing of their lumen are noted. Around the vessels there is perivascular infiltration consisting of lymphoid cells, macrophages, fibroblasts with an admixture of basophils in various stages of degranulation.

Symptoms of contact allergic dermatitis

Allergic dermatitis is characterized by true polymorphism of the rash, localized in areas exposed to the allergen. At the same time, patients with erythema with unclear boundaries, papules and edema have clinical manifestations characteristic of eczema (vesiculation, weeping, tendency to relapse). But they are less pronounced in allergic contact dermatitis.

In some patients, clinical manifestations extend beyond the zones of action of allergic agents. Subjective sensations are noted to varying degrees of severity: itching, burning, a feeling of heat in the affected areas. There have been cases of patients who experienced acute allergic contact dermatitis after using 33% sulfur ointment for scabies and treating the genital area with chlorhexidine solution.

Diagnostics and differential diagnosis

The disease should be distinguished from simple contact dermatitis and eczema.

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Treatment of contact allergic dermatitis

First, it is necessary to eliminate the cause of contact allergic dermatitis. In case of pronounced clinical manifestations, antihistamines (tavegil, fenistil, analergin, diazolin, suprastin, etc.) and hyposensitizing agents (calcium chloride or calcium gluconate, sodium thiosulfate), vitamins are prescribed. In severe cases, patients are hospitalized and systemic glucocorticosteroids are recommended.

External therapy is carried out taking into account the stage of the disease and the severity of the inflammatory process. In case of severe erythema, zinc oxide, white clay in the form of powders, water-shaken suspensions, zinc ointments (2-5%), creams and ointments containing GCS are prescribed. Of the local antipruritic agents, Fenistil gel has a good effect. In case of exudation, lotions are used, as well as aniline dyes, indifferent pastes. To resolve the process, ointments with a resorption effect are used (5-10% ichthyol, 2% sulfur-salicylic, 2% sulfur-tar).