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Allergic Contact Dermatitis Workup

  • Author: Daniel J Hogan, MD; Chief Editor: William D James, MD  more...
Updated: Aug 23, 2016

Approach Considerations

A guideline summary on allergy testing is available from the American Academy of Allergy, Asthma and Immunology, American College of Allergy, Asthma and Immunology (Allergy Diagnostic Testing: An Updated Practice Parameter).[18]

Go to Irritant Contact Dermatitis, Pediatric Contact Dermatitis, and Protein Contact Dermatitis for complete information on these topics.


Lab Studies

Potassium hydroxide preparation and/or fungal culture to exclude tinea are often indicated for dermatitis of the hands and feet. This will identify disorders such as tinea pedis.


Patch Testing

Patch testing[19, 20, 21] is required to identify the external chemicals to which the person is allergic. The greatest quality-of-life benefits from patch testing occur in patients with recurrent or chronic allergic contact dermatitis (ACD). Patch testing is most cost-effective and reduces the cost of therapy in patients with severe allergic contact dermatitis.

Patch testing should be performed by healthcare providers trained in the proper technique. Most dermatologists can perform patch testing using the TRUE test, which can identify relevant allergies in as many as one half of affected patients. More extensive patch testing is indicated to identify allergies to chemicals not found in the TRUE test. Such testing typically is available only in a limited number of dermatology offices and clinics.

The patch testing procedure is as follows:

  • Small amounts of appropriate labeled dilutions of chemicals are applied to the skin and occluded for 2 days
  • Patch tests may be left on for 3 days before removal
  • For reasons of scheduling, a chemical must remain under a skin patch for a minimum of 1 day to produce a positive patch test reaction 2-7 days following initial application
  • The patch test must be read not only at 48 hours, when the patch tests customarily are removed, but again between 72 hours and 1 week following initial application

Individuals with suspected allergic contact dermatitis without positive reactions on the TRUE test or with chronic dermatitis or relapsing dermatitis, despite avoiding chemicals to which they are allergic (identified on TRUE test), need additional patch testing. Many individuals have more than 1 contact allergy and may be allergic to 1 or more chemicals found on the TRUE test and on special allergen trays or series.

Testing reactions to more allergens increases accuracy of the diagnosis of allergic contact dermatitis. Selection of allergens for testing requires consideration of the patient's history and access to appropriate environmental contactants.

Certain chemicals (eg, neomycin) typically produce delayed positive patch test reactions at 4 days or later following initial application. A tendency exists for elderly patients to manifest positive patch test reactions later than younger patients. Do not perform patch testing on patients taking more than 15 mg/d of prednisone. Oral antihistamines may be used during the patch test period if required.

Angry back syndrome or excited skin syndrome may occur. If a patient has a large number of positive patch test reactions, retesting the patient sequentially to a small series of these allergens may be necessary to exclude nonspecific false-positive reactions. The syndrome most likely occurs in individuals who have active dermatitis at the time of patch testing or who have a strong positive patch test reaction, both of which may induce local skin hyperreactivity in the area where patches were applied.

Additional patch test series or sets include the following:

  • Corticosteroids, particularly tixocortol pivalate and budesonide
  • Ingredients in cosmetics not found in the TRUE test
  • Chemicals used in dentistry that may produce mucosal and lip dermatitis in dental clients or that may produce chronic dermatitis of the hands in dentists and dental team members
  • Chemicals used in hairdressing that may produce facial, ear, and neck dermatitis in clients or chronic hand dermatitis or eyelid dermatitis in hairdressers
  • Fragrances found in cosmetics and a wide range of consumer products

Important allergens not found in the TRUE test that are frequent causes of allergic contact dermatitis are as follows:

  • Acrylates used in dentistry, artificial nails, and printing
  • Chemicals used in baking
  • Pesticides (many cases of dermatitis attributed to pesticides result from other causes, particularly from plants such as poison ivy)
  • Chemicals used in machining, eg, cutting oils and fluids
  • Photographic chemicals used by photographers and photographic developers
  • Plants
  • Chemicals in plastics and glues
  • Chemicals found in rubber products not included in the TRUE test
  • Chemicals in shoes and clothing
  • Ultraviolet (UV) protective ingredients in sunscreens
  • Other chemicals producing photo allergic contact dermatitis
  • Miscellaneous allergens

The chemicals listed above are tested under Finn chambers, allergEAZE chambers, or the IQ Chamber patch test. In photopatch testing, the chemicals are applied in duplicate sets. One set receives 10 J/cm2 of UV-A (or 1 J/cm2 less than the minimum erythema dose, whichever is lowest) 24 hours after application of the allergens. The other series is protected from UV exposure to differentiate allergic contact dermatitis and photo-accentuated allergic contact dermatitis from photo-allergic contact dermatitis. Both sets are read at 48 hours after application, as well as at an additional time point as in routine patch testing.

The safety of patch testing in pregnancy has not been studied; however, the minute amounts of allergens applied appear unlikely to be absorbed in sufficient amounts to harm the fetus. Nonetheless, as with all treatments in pregnant women, the benefits of testing should be weighed against any potential, albeit undocumented, risk.


Repeat Open Application Test

For individuals who develop weak or 1+ positive reactions to a chemical, the repeat open application test (ROAT) is useful in determining whether the reaction is significant. ROAT is most useful when an individual has a 1+ reaction to a chemical found in a leave-on consumer product.

For example, an individual with a weak reaction to a preservative found in a moisturizer may apply the moisturizer twice a day for a week to the side of the neck or behind an ear; if clinical dermatitis does not develop, the 1+ reaction likely was not meaningful. Conversely, if dermatitis develops after a few days of repeated application of the suspected product, then the weak patch test reaction is highly relevant.


Dimethylgloxime Test

The dimethylgloxime test is a useful and practical way to identify metallic objects that contain enough nickel to provoke allergic dermatitis in individuals allergic to nickel. Dermatology staff may test suspected metal products in the office, or the individual may purchase a test kit and test objects at home or at work, particularly jewelry or metallic surfaces.

Other chemical tests are available for other suspected allergens (eg, formaldehyde, cobalt, chromate). Occasionally, chemical analyses may be necessary to determine whether a material contains a suspected allergen or to identify new unknown allergens.


Skin Biopsy

Skin biopsy may help exclude other disorders, particularly tinea, psoriasis, and cutaneous lymphoma. Skin biopsy of skin lesions of the palms and soles has several potential pitfalls, however.

The stratum corneum and epidermis are particularly thick on the palms and soles. This makes the histologic diagnosis of psoriasis more difficult and increases the possibility that the biopsy specimen will lack sufficient dermis for optimal diagnosis.

An overly deep skin biopsy of the thenar area can cut the motor nerve, which is the recurrent branch of the median nerve. A biopsy from the sole may leave a chronic painful scar on which the patient must walk.


Histologic Findings

The histology of allergic contact dermatitis is similar to that found in other forms of eczematous dermatitis. A pattern of subacute chronic dermatitis or acute dermatitis may be seen. The inflammatory infiltrate in the dermis predominately contains lymphocytes and other mononuclear cells.

Epidermal edema (ie, spongiosis and microvesicle formation) may be seen, but these changes may be absent in long-standing dermatitis in which thickening of the epidermis (acanthosis) with hyperkeratosis and parakeratosis may be seen in the epidermis and stratum corneum. Allergic contact dermatitis may provoke atypical T-cell infiltrates, simulating mycosis fungoides.

Contributor Information and Disclosures

Daniel J Hogan, MD Clinical Professor of Internal Medicine (Dermatology), Nova Southeastern University College of Osteopathic Medicine; Investigator, Hill Top Research, Florida Research Center

Daniel J Hogan, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Contact Dermatitis Society, Canadian Dermatology Association

Disclosure: Nothing to disclose.

Chief Editor

William D James, MD Paul R Gross Professor of Dermatology, Vice-Chairman, Residency Program Director, Department of Dermatology, University of Pennsylvania School of Medicine

William D James, MD is a member of the following medical societies: American Academy of Dermatology, Society for Investigative Dermatology

Disclosure: Nothing to disclose.


Donald Belsito, MD Professor of Clinical Dermatology, Department of Dermatology, Columbia University Medical Center

Donald Belsito, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Contact Dermatitis Society, Dermatology Foundation, New York County Medical Society, New York Dermatological Society, Noah Worcester Dermatological Society, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Barry E Brenner, MD, PhD, FACEP Professor of Emergency Medicine, Professor of Internal Medicine, Program Director for Emergency Medicine, Case Medical Center, University Hospitals, Case Western Reserve University School of Medicine

Barry E Brenner, MD, PhD, FACEP is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Chest Physicians, American College of Emergency Physicians, American College of Physicians, American Heart Association, American Thoracic Society, Arkansas Medical Society, New York Academy of Medicine, New York Academy of Sciences,and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Jeffrey P Callen, MD Professor of Medicine (Dermatology), Chief, Division of Dermatology, University of Louisville School of Medicine

Jeffrey P Callen, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, and American College of Rheumatology

Disclosure: Amgen Honoraria Consulting; Celgene Honoraria Safety Monitoring Committee

Simon K Law, MD, PharmD Clinical Professor of Health Sciences, Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine

Simon K Law, MD, PharmD is a member of the following medical societies: American Academy of Ophthalmology, American Glaucoma Society, and Association for Research in Vision and Ophthalmology

Disclosure: Nothing to disclose.

Mark Louden, MD Assistant Professor of Clinical Medicine, Division of Emergency Medicine, Department of Medicine, University of Miami, Leonard M Miller School of Medicine

Mark Louden, MD is a member of the following medical societies: American Academy of Emergency Medicine and American College of Emergency Physicians

Disclosure: Nothing to disclose.

R Scott Lowery, MD Associate Professor of Ophthalmology, Department of Pediatric Ophthalmology and Strabismus, University of Arkansas for Medical Sciences College of Medicine, Arkansas Children's Hospital

R Scott Lowery, MD is a member of the following medical societies: American Academy of Ophthalmology and Arkansas Medical Society

Disclosure: Nothing to disclose.

Joshua May, MD Bend Dermatology Clinic

Disclosure: Nothing to disclose.

John A Michael, MD

Disclosure: Nothing to disclose.

Christopher J Rapuano, MD Professor, Department of Ophthalmology, Jefferson Medical College of Thomas Jefferson University; Director of the Cornea Service, Co-Director of Refractive Surgery Department, Wills Eye Institute

Christopher J Rapuano, MD is a member of the following medical societies: American Academy of Ophthalmology, American Society of Cataract and Refractive Surgery, Contact Lens Association of Ophthalmologists, Cornea Society, Eye Bank Association of America, and International Society of Refractive Surgery

Disclosure: Allergan Honoraria Speaking and teaching; Allergan Consulting fee Consulting; Alcon Honoraria Speaking and teaching; RPS Ownership interest Other; Bausch & Lomb Honoraria Speaking and teaching; Merck Consulting fee Consulting; Bausch & Lomb Consulting; Merck Honoraria Speaking and teaching

Hampton Roy Sr, MD Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences

Hampton Roy Sr, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, and Pan-American Association of Ophthalmology

Disclosure: Nothing to disclose.

David Todd Schwartz, MD Associate Professor of Emergency Medicine, New York University School of Medicine; Attending Physician, Department of Emergency Medicine, Bellevue Hospital Center and New York University Medical Center

David Todd Schwartz, MD is a member of the following medical societies: American Academy of Emergency Medicine and American College of Emergency Physicians

Disclosure: Nothing to disclose.

Bradley D Shy, MD Staff Physician, Department of Emergency Medicine, Bellevue Hospital Center, New York University School of Medicine

Disclosure: Nothing to disclose.

Richard P Vinson, MD Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine; Consulting Staff, Mountain View Dermatology, PA

Richard P Vinson, MD is a member of the following medical societies: American Academy of Dermatology, Association of Military Dermatologists, Texas Dermatological Society, and Texas Medical Association

Disclosure: Nothing to disclose.

Jack L Wilson, PhD Distinguished Professor, Department of Anatomy and Neurobiology, University of Tennessee Health Science Center College of Medicine

Jack L Wilson, PhD is a member of the following medical societies: American Association of Anatomists, American Association of Clinical Anatomists, and American Heart Association

Disclosure: Nothing to disclose.

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Chronic stasis dermatitis with allergic contact dermatitis to quaternium-15, a preservative in moisturizer. Allergic contact dermatitis produces areas of erythema in areas of atrophie blanche and varicose veins.
Erythema multiformelike reaction that developed acutely following hair dying.
Allergic contact dermatitis to nickel in a necklace.
Severe allergic contact dermatitis resulting from preservatives in sunscreen. Patch testing was negative to the active ingredients in the sunscreen.
Onycholysis developing from allergic contact dermatitis to formaldehyde used to harden nails.
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