Contact Dermatitis in Patients with Venous Ulcers – and How to Prevent It?
The prevalence of chronic wounds increases with the rising average age, and for example, venous ulcers affect up to 2% of the global population. Materials used for wound coverage, however, present a risk for the development of contact dermatitis of allergic or irritant origin. The topic of contact dermatitis in patients with venous ulcers is covered in a review article published in the International Journal of Women’s Dermatology.
Introduction
Patients with chronic, poorly healing wounds are at increased risk of developing contact dermatitis because their skin loses its protective function. Allergic contact dermatitis can be caused in these individuals by relatively weak allergens. For example, parabens, which have a low sensitizing potential on healthy skin, pose up to an 11 times higher risk of sensitization in patients with venous ulcers. Increased risk of sensitization is also noted with neomycin and primarily affects older individuals.
Irritant and Allergic Origin of Contact Dermatitis
Contact dermatitis (CD) is usually categorized into two main types – irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD). Most issues (> 80%) fall into the ICD group, related to direct contact of the skin with an irritant substance. Any chemical substance can become a potential irritant if it acts on the skin for a long time. Manifestations of acute ICD are typically noticeable within minutes to hours of contact with the irritant, with delayed reaction occurring between 8-48 hours.
It is relatively challenging to distinguish chronic irritant CD from allergic CD in practice. ACD is considered a delayed hypersensitivity reaction depending on the strength of the allergen and the permeability of the skin barrier. An allergen can provoke a reaction within days or weeks, and clinical manifestations can include eczema, vesiculobullous manifestations, or other skin issues.
Role and Importance of Patch Testing in CD
Patch testing is the gold standard in the diagnosis of ACD. Evaluation of tests, which are usually done on the upper back or the inner side of the arm, occurs after the removal of patches with allergens and is repeated after 72–120 hours. Patients should monitor the area even after the evaluation due to potential delayed reactions.
However, the tests carry a high risk of false-negative results since they are conducted on intact skin. Therefore, in some cases, the skin is lightly disrupted before starting the test to simulate conditions closer to those of patients with venous ulcers.
The 15 main contact allergens in patients with chronic wounds include nickel, cobalt, neomycin, bacitracin, Peru balsam, rosin, chlorhexidine, certain corticosteroids, and others.
Selected Dressings and Their Risks
Hydrogels can cause both irritant and allergic CD. The cause of ICD can be the high water content in hydrogel dressings, leading to maceration and disruption of the skin barrier function. ACD is usually related to the propylene glycol content in hydrogel dressings.
Hydrocolloid dressings can cause contact dermatitis due to rosin content according to several studies, although this potential allergen is often modified with other chemicals.
Reports of contact dermatitis with the use of alginate and hydrofiber dressings containing calcium alginates and carboxymethylcellulose have been noted in limited amounts of clinical studies.
There is a described risk of allergic reaction with polyurethane foam dressings containing hydrocellulose. A 2015 study reported a 1.4% risk.
The application of topical antibiotics in the treatment of skin defects, including venous ulcers, is not recommended due to the risk of antibiotic resistance and the development of contact dermatitis. Commonly used antibiotics, such as neomycin, are among the main allergens in patients with venous ulcers and can be a significant cause of morbidity.
Natural products used in wound treatment, such as herbal products and dressings with honey or propolis, might be more accessible and cheaper than modern dressings, but their efficacy is often not well-documented. Some components, such as propolis, are also common allergens.
Conclusion
The goal of treating allergic and irritant contact dermatitis is to avoid the use of allergens and irritants and to suppress inflammation with topical or oral immunosuppressive medications. Knowledge of potential allergens and monitoring the composition of various dressings are crucial for doctors to use adequate covering materials when treating patients with venous ulcers. Patients should be advised to use emollients and other products without risky substances to protect their skin.
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Source: Alavi A., Goldenberg A., Jacob S. et al. Contact dermatitis: an important consideration in leg ulcers. Int J Womens Dermatol 2020; 7 (3): 298–303, doi: 10.1016/j.ijwd.2020.12.010.
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