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Paper text:
as lifestyles become more complex , the skin is exposed to an ever - increasing spectrum of chemical and biological allergens .
while the skin barrier is relatively impermeable to large molecules , contact allergens , because of their small size , easily penetrate the skin barrier and reach the living layers .
one of the extended applications of patch testing is whenever the physician suspects past or a recent history of superimposed acd .
when the existence of one or more positive reactions is found , relevance must then be determined .
the most important question is whether the reaction is a manifestation of the presenting dermatitis or the expression of an acd that occurred previously .
this prospective , observational study was conducted among 110 patients at the outpatient department of dermatology , manipal hospital , bangalore , between march 2009 and december 2010 .
subjects of any age with any form of psoriasis of more than six months duration who were unresponsive to conventional topical treatments were included .
pregnant women , patients with extensive psoriasis , current or recent dermatitis at patch test site and patients receiving oral prednisolone more than 20 mg / day or recent phototherapy were excluded from the study .
koh mount for fungal identification and skin biopsy were performed in some patients as part of diagnostic work up .
all patients were patch tested with the indian standard series ( iss ) including parthenium .
patch test readings were taken on day 2 ( 48 hours ) and day 4 ( 96 hours ) and interpreted according to the international contact dermatitis research group criteria .
the relevance of positive reactions was assessed and explained to patients as being related to the present problem or not and for cautioning against future exposure [ figures 1 and 2 ] .
the relevance of positive allergens was recorded as definite , probable , possible , past , or unknown .
current relevance was defined as present relevance ( definite , probable , or possible ) .
relevance was considered definite if a use test with the item containing the suspected allergen was positive or a positive patch test to the object / product was observed . for use test , the patient was asked to use the suspected substance in the same way as when the dermatitis developed .
for example , if a hand cream is suspected , it is applied over a small marked area ( 1  1 cm ) on the hand for 1 week .
if an eczematous skin reaction occurs during the test period , the test is considered positive .
relevance was considered probable if the substance identified by patch testing could be verified as present in the unknown skin contactants of the patient .
relevance was considered possible if the patient was exposed to circumstances in which skin contact with materials unknown to contain the allergen would likely occur .
the current relevance was tabulated by adding the number of patients with the relevance coded as definite , probable , or possible and converting this to a percentage of patients with a positive test result for the allergen .
source of exposure for each relevant positive allergen was determined based on discussion with the patient .
use test was performed in 10 patients and patch test with patient 's own product  as is  was done in 24 patients .
positive iss antigen reactions in those who had a positive use test or a positive  as is  were grouped as those reactions with a definite relevance . in those patients who had not undergone
a use test/as is  patch test , positive iss antigen reactions were grouped as those with a possible or probable relevance or past or unknown relevance .
a taxi - driver with chronic , recalcitrant palmar psoriasis was patch tested a taxi - driver with chronic , recalcitrant palmar psoriasis was patch tested the statistical software namely spss 15.0 , stata 8.0 , medcalc 9.0.1 , and systat 11.0 were used for the analysis of the data and microsoft word and excel have been used to generate graphs and tables .
the age group ranged from 6 to 70 years with an average of 40 years .
most males were in the age group of 21 to 30 years and most females in 51 to 60 years .
the duration of illness ranged from two months to 20 years with an average of four years . for most men ,
the duration of illness was one to two years and in case of women , it was more than two years .
20% of subjects had intense pruritus over legs , palms , and soles ; 13.6% had burning sensation over palms and soles ; 9.1% had lichenification over the legs ; and 7.3% had hyperpigmentation over the legs .
palmoplantar psoriasis ( 32.7% ) was the most commonly patch - tested type of psoriasis [ table 1 ] .
diagnosis of palmoplantar psoriasis was made clinically by the presence of psoriasiform , scaly plaques with well - demarcated margins ; presence of papules and plaques elsewhere in the body that showed a positive auspitz sign ( this was observed in 28 ( 25.4% ) patients ) ; nail changes like pitting and subungual hyperkeratosis . in doubtful circumstances ,
tinea manuum and pedis and atopic dermatitis were ruled out on clinical grounds and by performing 10% koh mount and serum ige tests .
personal history of atopy was found in 12 patients ( 10.9% ) , family history of atopy in five patients ( 4.5% ) who had a final diagnosis of psoriasis .
different types of psoriasis that were patch tested the commonly tested positive allergens were fragrance mix ( 13.6% ) , nickel sulphate ( 9.1% ) , parthenium ( 6.4% ) , and balsam of peru ( 5.5% ) [ table 2 ] .
47.3% of subjects showed a positive reaction on day 2 and 42.7% of the subjects showed positive reaction to one or more allergens on day 4 .
28.2% showed reaction to only one allergen ; 8.2% to two allergens ; 1.8% to three allergens , and 4.5% to more than three allergens .
number of patients tested for positive for each antigen in the current study , fragrance mix , ppd ( paraphenylenediamine ) , paraben mix , lanolin , black rubber mix , para - tertiary - butyl formaldehyde resin , mercapto mix , chlorocresol , and cobalt chloride showed 100% current relevance [ table 3 ] , followed by balsam of peru ( 83.3% ) , nickel sulfate ( 80% ) , and parthenium ( 71.4% ) .
nitrofurazone had 100% past relevance followed by neomycin sulfate ( 50% ) and gentamicin sulfate ( 50% ) . under current relevance ,
ppd , paraben mix , chlorocresol , black rubber mix , neomycin sulfate , and gentamicin sulfate had 100% definite relevance [ table 4 ] , followed by nickel sulfate ( 75% ) and fragrance mix ( 73.3% ) .
cobalt chloride had a high ( 100% ) probable relevance and mercapto mix had a high ( 100% ) possible relevance .
overall relevance of positive antigens present relevance of positive antigens allergens that were most commonly relevant were those that are found in different topical products like fragrances , topical medications , and preservatives [ table 5 ] .
these allergens are often found in cosmetic products or healthcare products and hence form the major sources of allergens in patients with psoriasis .
any chronic dermatosis such as psoriasis can be complicated by contact dermatitis due to an impaired cutaneous barrier .
pre - existing or concomitant constitutional and/or irritant contact dermatitis damages the skin , affecting its barrier function and producing increased opportunities for allergen absorption and secondary sensitization .
the extent to which contact allergens play a role in the etiology of psoriasis has always been contemplated .
it has been suggested that acd is uncommon in psoriasis.[16 ] some studies say that acd has been under - represented in patients with psoriasis .
other studies have observed positivity in 20 to 25% of patients with psoriasis.[391517 ] one study showed no difference in the frequency of allergic reactions between atopics , healthy persons , or psoriatics , whereas henseler and christophers calculated that acd was 3 times less frequent in patients with psoriasis compared with a control group .
another study by stinco et al . revealed that the number of positive patch tests in patients with psoriasis were similar to that in normal population , nickel being the commonest allergen in both groups , which was in agreement with other studies .
nickel sulfate , coal tar , dithranol , and fragrance mix were the most common allergens in most studies.[38915182021 ] this study reveals that 47/110 ( 42.7% ) of the subjects had a positive patch test to one or more allergens .
fragrance mix , nickel sulfate , parthenium , and balsam of peru were the most common sensitizers .
fragrance mix showed 100% current relevance and nickel sulfate showed 80% current relevance to the existing dermatitis .
relevance and avoidance of these allergens can be tricky when one considers the large variety of products each person uses on a daily basis and the choices available .
it is possible that careful screening of skin products and avoidance of the selected antigens may alleviate chronic , recalcitrant psoriasis .
patients confirmed as having positive and relevant contact allergy have been shown to have a significant improvement in both perceived eczema severity and dermatology life quality index score two months after patch testing .
acd significantly affects quality of life ( qol ) , especially when it affects the hands , face or is occupationally related .
outcomes in patients with acd were improved by early diagnosis and subjects enjoyed their best qol six to twelve months after patch testing .
patch testing and interpretation have been found to bring about greater improvement in the disease severity index and percentage disease activity than diagnosis without patch testing .
patch testing was found to be the most cost - effective in patients with a disease duration of two months to one year .
to conclude , secondary contact dermatitis is common in patients with psoriasis and patch testing is necessary to determine the triggering or aggravating factors in these patients , to avoid sensitizers and to improve qol .
background : psoriasis may be complicated by contact dermatitis due to an impaired cutaneous barrier . 
 patch testing helps elucidate sensitizers if any.aims:to determine the prevalence and relevance of secondary contact dermatitis in subjects with psoriasis.materials and methods : patch testing with indian standard series was done and readings interpreted after 48 and 96 hours.results:among 110 subjects 47 ( 42.7% ) showed reactions to at least one antigen . 
 fifteen ( 13.6% ) reacted to fragrance mix , 10 ( 9.1% ) to nickel sulfate , seven ( 6.4% ) to parthenium , and six ( 5.5% ) to balsam of peru . 
 palmoplantar psoriasis was the commonest type of psoriasis patch tested . 
 fragrance mix was the commonest antigen showing 100% current relevance as an aggravating factor of psoriasis . 
 cosmetics , beauty preparations , skin and healthcare products followed by topical medications were found to be the most common sources of the patch test positivity.conclusions:secondary contact dermatitis is common in patients with psoriasis . 
 patch testing is necessary to determine the triggering or aggravating antigens in these patients to avoid sensitizers and improve quality of life .