From the Guidelines
Allergic contact dermatitis typically does not blanch when pressure is applied. This is due to the complex tissue changes involved in the condition, including edema and cellular infiltration, which are a result of a delayed hypersensitivity reaction (type IV) to an allergen that contacts the skin 1. The inflammation in allergic contact dermatitis is characterized by redness, swelling, vesicles, and sometimes blistering, and is distinct from conditions where redness is primarily due to dilated blood vessels, such as urticaria (hives), which typically do blanch with pressure. Some key features of allergic contact dermatitis include:
- Well-demarcated areas of inflammation corresponding to allergen exposure sites
- Intense itching
- Possibly vesicles or bullae in severe cases
- Non-blanching quality of the inflammation, which can help differentiate it from other skin conditions. According to the British Association of Dermatologists' guidelines for the management of contact dermatitis 2017, the condition can be classified into different reaction types, including allergic contact dermatitis, which involves sensitization of the immune system to a specific allergen or allergens with resulting dermatitis or exacerbation of pre-existing dermatitis 1.
From the Research
Allergic Contact Dermatitis Characteristics
- Allergic contact dermatitis (ACD) is a T-cell-mediated skin inflammation resulting from the priming and expansion of allergen-specific CD4+ and CD8+ T cells 2.
- The clinical condition is characterized by local skin rash, itchiness, redness, swelling, and lesions, being mainly diagnosed by the patch test 2.
- ACD is the most prevalent occupational disease and the most common form of immunotoxicity in humans 2.
Symptoms and Diagnosis
- Symptoms of ACD include local skin rash, itchiness, redness, swelling, and lesions 2.
- Diagnosis of ACD relies on clinical presentation, thorough exposure assessment, and evaluation with techniques such as patch testing and skin-prick testing 3, 4.
- Other diagnostic tests can be used to help diagnose ACD and identify the causative allergens, including photopatch test, skin tests for detecting immediate contact reactions, serum allergen-specific IgE test, and qualitative and quantitative testing of allergen in the suspected materials patients exposed to and challenge test 4.
Treatment and Management
- Management of ACD is based on patient education, avoidance strategies of specific substances, and topical treatments; in severe or recalcitrant cases, systemic medications may be needed 3.
- Avoiding the exposure to the triggering allergen is the mainstay of treatment to prevent future flares 2.
- Standard of care interim treatments such as steroid creams or ointments, barrier creams, and moisturizers are strongly recommended to alleviate symptoms 2.
Impact on Wound Healing
- ACD can disrupt the normal wound repair process due to prolonged inflammation and immune dysregulation 5.
- ACD is associated with higher levels of inflammatory markers, altered cellular responses, and delayed wound closure 5.
- The study demonstrates that ACD exerts a substantial impact on the inflammatory response, cellular components, and wound healing parameters in the context of skin trauma 5.
Blanching
- There is no direct evidence in the provided studies that allergic contact dermatitis blanches. The studies focus on the characteristics, symptoms, diagnosis, treatment, and management of ACD, as well as its impact on wound healing, but do not mention blanching as a symptom or characteristic of ACD.