Allergic Contact Dermatitis Diagnosis

Allergic Contact Dermatitis (ACD) Diagnosis

• ACD is a potential diagnosis for patients with eczematous dermatitis, but also important to consider in various dermatitis types, even in atopic, erythroderma, or generalized dermatitis cases persistent despite standard treatments.
• ACD characteristics are not always obvious. Bilateral exposure doesn't always mean bilateral symptoms, and uniform exposure doesn't always result in uniform affected areas.
• ACD can affect the palms and soles.
• Initial diagnosis involves a detailed patient history, focusing on: present illness, sites of onset, topical treatments (prescription/OTC), skin conditions, atopy, general health, use of personal care products, and hobbies/occupational activities. Thorough occupational history is crucial, especially for those with frequent hand washing, glove use, or chemical exposure.
• Diagnosis is usually based on history, physical exam, and patch test results.
• Clinical workup may include labs (CBC, eosinophilia) or skin biopsy in certain cases, where histological e findings like eosinophilic spongiosis, multinuclerate dermal dendritic fibrohistiocytic cells, acanthosis, and lymphocytic infiltrate can be indicative of ACD.
• Skillful analysis of the patient's exposure history, along with the distribution of dermatitis, can sometimes identify the allergens.
• Patch testing is usually necessary to identify the specific causative allergens.
• A topographic approach (based on the distribution of dermatitis) and an allergen-specific approach (based on known trends of dermatitis in relation to allergens) to guide the patch test are most useful,
• Dermatitis distribution is often the most important factor to the diagnosis.
• Periumbilical/infraumbilical eczema may correlate with metal snaps or belt buckles. Hairline and areas behind ears with eczema suggest hair product allergies (shampoo, dye, etc). Dorsum of feet eczema can indicate shoe materials (leather, dyes, rubber), whereas weight-bearing foot areas can suggest insole/sole materials (rubber, adhesive). Facial, eyelid, lip, and neck eczema suggests cosmetic-related contact allergy. Patch testing is always needed, even in these cases, to confirm positive allergens. -Distribution patterns may be misleading (especially in ectopic or airborne ACD). Ectopic ACD can be from autotransfer or heterotransfer (connubial/consort ACD) - in one case, the allergen is transerred by the patient's fingers to other sites, and, in the other case the allergen is transferred to the patient by another person.