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The mystery of allergic contact dermatitis: Why is it so difficult to diagnose?
Allergic Contact Dermatitis (ACD) is a type of dermatitis caused by contact with allergens. The symptoms of this type of dermatitis are similar to those of irritant contact dermatitis, making diagnosis more difficult. According to various surveys, allergic contact dermatitis is one of the most common manifestations of human immunotoxicity, although its incidence is lower than irritant contact dermatitis. Due to its allergic nature, the pathogenesis of this dermatitis is complex, involves many subtle levels of control, and centers on the interaction between immunoregulatory cytokines and specific subsets of T lymphocytes.
Symptoms and manifestations
The first sign of allergic contact dermatitis is a rash or skin lesions on the skin after exposure to the allergen. Depending on the substance causing the allergy, the rash may ooze, drain, or crust over, or it may become raw, scaly, or thickened. It is important to note that these skin lesions may sometimes not be in the form of a rash and may include other manifestations such as erythema, blisters, or pustules.
Allergic contact dermatitis usually occurs within 24 to 48 hours after exposure to the allergen. Symptoms include itching, redness, and localized swelling. If ignored, the skin may become dark, leathery, or cracked state.
Reason
Allergens in allergic contact dermatitis include a variety of common substances, such as:
- Bacitracin
- Chromium
- Cobalt
- Fragrance mix
- Nickel
These substances often appear in daily necessities, including cosmetics, clothing, jewelry, etc., posing a risk of widespread exposure.
Mechanism
The occurrence of allergic contact dermatitis goes through two key stages: the induction stage and the initiation stage. During the induction phase, after the body is exposed to the allergen, the immune system processes and presents it in preparation for an allergic reaction. In the triggering stage, when exposed to the same allergen again, T cells can directly recognize the allergen and generate an immune response at the contact site.
This reaction is dominated by directly mediated T cells and belongs to Type IV hypersensitivity reaction. This process is controlled by a variety of cytokines and chemical factors.
Diagnosis
Diagnosis of allergic contact dermatitis mainly relies on clinical examination and medical history. In some cases, a doctor can make the correct diagnosis based on symptoms and the appearance of the rash. For chronic or intermittent rashes, further testing may be required such as a patch test. This test involves applying a small amount of a potential allergen to the skin and watching for a skin reaction after a certain amount of time.
Treatment
The most effective way to relieve the symptoms of dermatitis is to avoid exposure to allergens. The first step in treatment is to carefully identify the substance causing the problem and, if necessary, administer the corticosteroid corticosteroids. Typically, severe cases are treated with systemic corticosteroids.
Epidemiology
The incidence of allergic contact dermatitis is quite high, affecting up to 20% of the population. For people who are already sensitive to one allergen, the risk of sensitivities to other substances is also increased. Additionally, studies have found that women are more likely than men to develop allergic contact dermatitis.
Although the diagnosis and treatment of allergic contact dermatitis have gradually matured, why are so many patients still being diagnosed?
