title: Patch Test as a Diagnostic Tool in Hand Eczema.
abstract: BACKGROUND
  Allergic contact dermatitis is an important cause of hand eczema. Patch testing is the only investigation available to prove the diagnosis of allergic contact dermatitis. Exposures to allergens differ according to geographical, occupational, economic and social factors. Accordingly, patterns of allergic contact dermatitis differ in different parts of the world and different regions of the same country.
  
  
  OBJECTIVE
  To study the causes of allergic contact dermatitis in adult patients with hand eczema with the help of patch testing.
  
  
  METHODS
  This was a cross-sectional study involving 54 hand eczema patients conducted between October 2013 and June 2015, at a tertiary care centre in Southern India. After a detailed history including history of occupational exposure and detailed examination, patch test was done on these patients with Indian standard series. The patches were removed after 48 hours. Another reading was taken after 72 hours. The readings were interpreted according to International Contact Dermatitis Research Group criteria and noted down. The data were summarized using mean and standard deviation for continuous variables and percentages for categorical and dichotomous variables. The test of association was done with Fisher's-exact test.
  
  
  RESULTS
  Hyperkeratotic hand eczema was the commonest morphological type (29%), followed by discoid eczema. Pompholyx was significantly more common among patients with history of atopy. A total of 20 patients (37%) showed patch test positivity to a total of 25 allergens. Nickel was the most common allergen (11.11%) followed by para-phenylenediamine (PPD) (7.4%). Nickel (6 patients) and cobalt (3 patients) were the common allergens among women, while potassium dichromate (3 patients) and parthenium (2 patients) were the common allergens among men. Potassium dichromate allergy was significantly more common among masons and PPD allergy was significantly more common among hair dye users. Discoid pattern of hand eczema was common among patients with allergy to potassium dichromate.
  
  
  CONCLUSIONS
  Majority of the cases of hand eczema are not due to allergic contact dermatitis. History of atopy is common among patients with pompholyx. Allergic contact dermatitis due to nickel remains a common cause of hand eczema.
authors.affiliation: Junior Resident, Department of Dermatology, Venereology and Leprosy, Pondicherry Institute of Medical Sciences , Pondicherry, India .
authors.forename: Natarajan
authors.initials: N
authors.lastname: Vigneshkarthik
authors.affiliation: Associate Professor, Department of Dermatology, Venereology and Leprosy, Pondicherry Institute of Medical Sciences , Pondicherry, India .
authors.forename: Satyaki
authors.initials: S
authors.lastname: Ganguly
authors.affiliation: Professor and Head, Department of Dermatology, Venereology and Leprosy, Pondicherry Institute of Medical Sciences , Pondicherry, India .
authors.forename: Sheela
authors.initials: S
authors.lastname: Kuruvila
keywords: Allergic contact dermatitis; Nickel; Para- phenylenediamine; Potassium dichromate