Changes

**Mononuclear cells

**Mononuclear cells

**If chronic, epidermal hyperplasia

**If chronic, epidermal hyperplasia

**May involve [[Eosinophils - WikiBlood|eosinophils]]

**May involve [[Eosinophils|eosinophils]]

===Atopy===

===Atopy===

*Microscopically:

*Microscopically:

**Hyperplastic superficial perivascular dermatitis

**Hyperplastic superficial perivascular dermatitis

**Oedema, [[Mast Cells - WikiBlood|mast cells]], [[Basophils|basophils]], [[Eosinophils - WikiBlood|eosinophils]], [[Lymphocytes|lymphocytes]], histiocytes

**Oedema, [[Mast Cells - WikiBlood|mast cells]], [[Basophils|basophils]], [[Eosinophils|eosinophils]], [[Lymphocytes|lymphocytes]], histiocytes

**Fibropruritic nodules covered by hyperplastic epidermis

**Fibropruritic nodules covered by hyperplastic epidermis

**Similar to [[Skin Immunologic - Pathology#Pemphigus|Pemphigus vulgaris]]

**Similar to [[Skin Immunologic - Pathology#Pemphigus|Pemphigus vulgaris]]

*Microscopically:

*Microscopically:

**Bullae containing fibrin, [[Neutrophils|neutrophils]] or [[Eosinophils - WikiBlood|eosinophils]]

**Bullae containing fibrin, [[Neutrophils|neutrophils]] or [[Eosinophils|eosinophils]]

**Basement membrane forms floor of bullae and roof is lined with basal cells

**Basement membrane forms floor of bullae and roof is lined with basal cells

*Bullae may rupture -> ulcers

*Bullae may rupture -> ulcers