Interstitial Dermatitis is a histopathological pattern of dermal inflammation characterized by a diffuse, band-like infiltrate of inflammatory cells—including lymphocytes, histiocytes, and sometimes mast cells—predominantly occupying the interstitial connective tissue between collagen bundles, typically associated with conditions such as erythema chronicum migrans or drug reactions, and distinguished from other inflammatory patterns by the absence of confluent perivascular aggregation and the lack of significant epidermotropism.