The typical symptoms of allergic contact dermatitis include a red rash, often without clearly defined edges; swelling; itching; and dry skin. On physical examination, this condition can present as either acute or chronic. Acute type is marked by erythematous, edematous, or urticarial appearing papules, plaques, vesicles and bullae that become increasingly eczematous and weeping. In areas with thinner skin like eyelid, penis, and scrotum, lesions are more edematous, with fewer superimposed vesicles. Intense pruritus can lead to secondary changes of excoriation; and subsequent impetiginization may be observed. With persistent or repeated exposure, sub-acute or chronic condition may develop. In sub-acute type, the skin remains erythematous and edematous as vesicles are replaced by erosions, oozing, crusting, and desquamation. On chronic exposure, the skin becomes dry, thick, and scaly with dermal infiltration, lichenification, and fissuring.

The inflammatory response is typically localized to areas directly in contact with the allergen and is well-demarcated, however, it can also be more widespread. The investigators have suggested that allergic contact dermatitis is well known for its ability to extend beyond areas of direct contact. This feature distinguishes it from irritant contact dermatitis. 1-4

Furthermore, some patients may have non-eczematous symptoms of contact allergic reactions which include erythema multiform-like reactions; pigmented purpura or pigmented contact dermatitis; lichen planus-like or lichenoid contact reactions in mucosa to dental allergens; bullous, papular-nodular and pustular reactions, especially to metal; lymphomatoid or primarily dermally localized variants; primarily edematous reactions; granulomatous reactions to metal salts and scleroderma-like lesions. 2

References

1. Murphy PB, Hooten JN, Atwater AR. Allergic Contact Dermatitis. [Updated 2019 Feb 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532866/
2. Brasch J, Becker D, Aberer W, et al. Guideline contact dermatitis: S1-Guidelines of the German Contact Allergy Group (DKG) of the German Dermatology Society (DDG), the Information Network of Dermatological Clinics (IVDK), the German Society for Allergology and Clinical Immunology (DGAKI), the Working Group for Occupational and Environmental Dermatology (ABD) of the DDG, the Medical Association of German Allergologists (AeDA), the Professional Association of German Dermatologists (BVDD) and the DDG. Allergo J Int. 2014;23(4):126–138.
3. Weintraub GS, Lai IN, Kim CN. Review of allergic contact dermatitis: Scratching the surface. World J Dermatol. May 2, 2015;4(2):95-102.
4. InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. Allergic contact dermatitis: Overview. 2017 Jul 13. Available from: https://www.ncbi.nlm.nih.gov/books/NBK447113/