Allergic contact dermatitis
- It is often not possible to differentiate allergic contact dermatitis from other types of dermatitis on the basis of clinical presentation alone.
- The diagnostic cornerstones are established contact allergy, clinical picture of an eczema and temporally-related exposure to the allergen in question.
- The possibility of allergic contact dermatitis should be borne in mind where dermatitis is not resolving despite appropriate treatment.
- Delayed cell-mediated allergy (skin contact allergy)
- Usually results from a long-standing exposure.
- The most common causative agents are nickel (picture (Nickel allergy)) as well as perfumes and preservatives used in cosmetics and hygiene products.
- Other causative agents include chemicals found in rubber, ingredients of plastics and glues (picture (Contact allergy)), chromium and cobalt compounds as well as ingredients used in skin care products.
- The site of the rash should prompt a suspicion of allergic contact dermatitis, particularly when located at the following sites:
- armpits (deodorants)
- hands and wrists (metal, leather, working tools, chemicals; picture (Contact allergy)).
- Allergic dermatitis may, however, occur anywhere on the body. Typical sites include:
- face (pictures (Allergic perioral dermatitis) (Neomycin allergy)) and neck (picture (Patchy dermatitis on the female neck); skin care products, cosmetics)
- waist (leather, metal; pictures (Contact allergy) (Nickel allergy reaction on the skin of the back))
- gluteal cleft (haemorrhoid creams and suppositories)
- thighs and legs (socks, rubber boots, topical treatments for leg ulcers)
- feet (metals, rubber, leather, dyes, contact glue, chromium, antimycotics).
- Patch testing is usually not indicated if the history clearly identifies the causative allergen, for example nickel.
- The diagnostics of skin contact allergy and allergic dermatitis use epicutaneous tests (patch testing (Diagnostic tests in dermatology)), which demonstrate possible sensitisation to allergens.
- However, a positive test result does not always prove the causal relationship with the patient’s dermatitis.
- Testing is carried out and interpreted by a dermatologist.
- The definitive treatment of allergic contact dermatitis is the avoidance or removal of the allergen (personal protective equipment, changing substances or methods used at the workplace, change of employment).
- Topical glucocorticoid creams
- Immunosuppressive medication is used occasionally in chronic cases at the discretion of a dermatologist.
- Treatment of allergic hand dermatitis: see (Hand dermatitis).
- Moderately potent to potent glucocorticoid creams once or twice daily until the skin has healed, for 2–6 weeks as appropriate to the severity of dermatitis. A follow-up appointment is indicated if the condition has not resolved.
- In acute vesicular dermatitis relief can often be obtained with moist compresses (10–20 minutes twice or thrice daily).
- In cases of severe and spreading allergic dermatitis a short course of systemic glucocorticoids may be indicated, e.g. prednisolone 20–40 mg once daily for 1–2 weeks.
- Antimicrobials are very rarely needed in allergic dermatitis, and they do not replace topical treatment. If the rash is clearly infected (picture (Hand dermatitis in a patient with atopy)), an antimicrobial may be indicated (cephalexin 500 mg three times daily for 7–10 days).
Immediate contact dermatitis
- Based on an immediate, IgE-mediated allergy
- Contact urticaria and protein contact dermatitis
- Redness, pruritus and/or urticaria develop immediately (less than 30 minutes) at the site of the allergen contact. Allergens include natural rubber (latex), cat or dog (dander or hair), root and other vegetables.
- Clearly more rare than allergic contact dermatitis, but in its chronic state its appearance may resemble that of allergic dermatitis.
- Particularly severe and extensive cases as well as chronic forms of the conditions
- Patch testing and the verification of diagnosis
- A suspicion of occupational allergic contact dermatitis or hand dermatitis
1. Johansen JD, Aalto-Korte K, Agner T et al. European Society of Contact Dermatitis guideline for diagnostic patch testing - recommendations on best practice. Contact Dermatitis 2015;73(4):195-221. [PMID:26179009]
2. Fonacier L, Bernstein DI, Pacheco K et al. Contact dermatitis: a practice parameter-update 2015. J Allergy Clin Immunol Pract 2015;3(3 Suppl):S1-39. [PMID:25965350]
3. Boonstra MB, Christoffers WA, Coenraads PJ et al. Patch test results of hand eczema patients: relation to clinical types. J Eur Acad Dermatol Venereol 2015;29(5):940-7. [PMID:25220568]
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