How to Diagnose Contact Dermatitis?

Author: V. Dimov, M.D., Allergist/Immunologist, Assistant Professor, University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist; Jeffrey R. Stokes, M.D., Associate Professor of Medicine, Creighton University Division of Allergy & Immunology

A 54-year-old female is referred by her dermatologist for an allergy evaluation for suspected contact dermatitis. She complains of "eczema" consisting of patches affecting both palms for the last 2 years. The rash barely responded to steroid cream and resolved completely after direct steroid injections. The lesions recurred several months later.

Past medical history (PMH)

Negative PMH.



Physical examination

Stable vital signs (VSS). The patient has a red scaly patch affecting the palmar surface of the right hand, 4 x 5 cm in size. A red patch affecting the palmar surface of the left hand, 2 x 1 cm in size (after steroid injections a month ago).

What is the most likely diagnosis?

Contact dermatitis.

The patient reports that she plays golf and the lesions are in the distribution of the area where the golf pole comes in contact with the skin. She does not play golf during the winter however but the lesions persist year-round.

What type of allergy is contact dermatitis?

Type IV, delayed hypersensitivity according to ACID classification.

This is a mnemonic for Gell and Goombs classification of hypersensitivity reactions: ACID

Anaphylaxis, angioedema, asthma, type I
Cytotoxic, antibody-mediated, type II, e.g AIHA, ITP, Graves'
Immune complex disease (CIC), type III, e.g. GN, serum sickness
Delayed, cell-mediated, type IV, e.g. contact dermatitis

The etiology of contact dermatitis is either allergic contact dermatitis (20% of cases) or irritant contact dermatitis (80% of cases).

The skin reaction to poison ivy or poison oak is a classic example of allergic contact dermatitis.

How do you test for contact dermatitis?

The most established test for contact dermatitis is skin patch testing. The patient is advised to take a shower the day before the test. Two patches are placed on the back. The patient should not take a bath of the whole body until test is read 48-72 hours later.

The patient should remove the patch at home before driving to the clinic. This time period of 30-60 minutes allows the surrounding nonspecific erythema (from the patch) itself to subside. The test area should be examined again 72-96 hours later to detect any delayed skin reaction.

A commercially available kit is the thin layer rapid use epicutaneous test (T.R.U.E. Test). The T.R.U.E. test manufacture website provides useful patient information handouts on avoidance of specific contact allergens.

The patch test for contact dermatitis is expensive. The cost is $30 per potential allergen, and a 20-allergen TRUE test would cost around $160-600. The CPT code is 95044, it is paid only contact dermatitis is listed as ICD-9 code for the visit (source: A typical charge is in the range of $160 (professional fee of $40, facility fee $120).

People can develop contact allergic dermatitis to topical steroids, a 20-allergen T.R.U.E. test does not include steroids, the 50-test includes 3.

A patient would need a hyperadhesive tape to hold the 50-allergen T.R.U.E. test on the back for diagnosis of contact dermatitis, otherwise it peels off.

Related Reading

Guidelines for the Management of Contact Dermatitis: an Update. J. Bourke; I. Coulson; J. English. The British Journal of Dermatology, Medscape, 06/02/2009.
Allergic skin diseases. Luz S. Fonacier, MD, Stephen C. Dreskin, MD, PhD, Donald Y.M. Leung, MD, PhD. The Journal of Allergy and Clinical Immunology, Volume 125, Issue 2, Supplement 2 , Pages S138-S149, February 2010 (PDF).
Cell phone contact dermatitis due to nickel allergy. ConsultantLive.
Cellphone contact dermatitis with nickel allergy. CMAJ • January 1, 2008; 178 (1).
In people with nickel allergies, cellphones can cause an allergic reaction. NYTimes, 2010.
Contact Dermatitis: A Learning Module by AAMC
Least-Welcome Sign of Summer - Poison Ivy - WSJ, 2010,
Patch testing to metal implants. AAAAI - Ask the Expert, 2011.
Post-Traumatic Basal Cell Carcinoma Associated With Patch Testing - with strongly positive reaction to gold. Actas Dermo-Sifiliogr√°ficas (English Edition), 2009.
Harry Potter star Daniel Radcliffe was allergic to wizard' glasses - the frames contained nickel
Thin-Layer Rapid-Use Epicutaneous Test (patch test) misses allergens in 12.5% of patients with contact dermatitis

Video Lectures

Contact Dermatitis. Paul Dowling, MD. Conferences Online For Allergy. Children's Mercy Hospitals & Clinics, July 11, 2008.


FIT Corner Questions. Chapter 87 of the 6th edition of Middleton’s Allergy Principles and Practice, edited by N. Franklin Adkinson, et al. January 31, 2007. Chapter 87: Contact Dermatitis.
Review Questions: Pediatric Allergy: Principles & Practices, Donald Y.M. Leung, et al., Chapter 55: Contact Dermatitis

Published: 07/12/2008
Updated: 03/08/2012

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