Causal agents of photoallergic contact dermatitis diagnosed in the national

institute of dermatology of Colombia

Edna Rodrıguez, Martha Cecilia Valbuena, Maritza Rey, Luisa Porras de Quintana

Centro Dermatologico Federico Lleras Acosta, ESE Bogota, Colombia

Objective: To describe and identify the photoallergens

causing photoallergic contact dermatitis in the popula-

tion attending the outpatient clinic of the Centro

Dermatologico Federico Lleras Acosta (CDFLLA),

the National Institute of Dermatology of Colombia.

Materials and methods: Eighty-two patients with clin-

ical diagnosis of photoallergic contact dermatitis enter

the study. These patients attended the CDFLLA

between August 2001 and May 2003. Photopatch tests

were performed using the standard series of sunscreens

(Chemotechnique Diagnostics) and 6-methylcoumarin.

Cetyl alcohol, phenoxyethanol, methylparabene, pro-

pylene glycol, triethanolamine, propylparabene, tri-

chlorocarbanilide and dichromate were also included.

The allergens were applied in duplicate on the healthy

skin of the back and covered with opaque tape with-

drawn 24 h later, the panel on the right was irradiated

with an ultraviolet A dose of 5 J/cm2. The tests were

read 24 h after the application of the allergens, 24 and

72 h post-irradiation. The readings were assessed ac-

cording to the visual scoring system recommended by

the International Contact Dermatitis Research Group.

Results: Twenty-six patients (31.7%) showed positive

photopatch test responses to one or several allergens.

Four of them showed positive results to three compo-

nents of the series and four patients to two components.

Thirty-eight photoallergic and 18 allergic reactions

were observed. Ultraviolet filters were the substances

which more frequently produced positive photopatch

test responses (30.5%). The most common ultraviolet

filter photoallergen was benzophenone-3 with 22/82

positive results (26.8%), followed by octyl metho-

xycinnamate (8/82), benzophenone-4 and mexenone

(2/82), phenylbenzimidazole sulphonic acid, methyl-

benziliden camphor and octyl dimethyl PABA (1/82).

One patient showed a photoallergic response to 6-

methylcoumarin. There was a concordance between the

allergen which elicited the positive response and the use

of different substances which contained that molecule

among its compounds in 17 patients (65.3%). 19.5% of

the patients (16/82) showed positive results to one or

several allergens in the irradiated panel as well as in

the unirradiated control site. These cases were diag-

nosed as contact allergy, probably caused by aero-

allergens, presenting a natural history and a clinical

picture similar to photocontact allergy. The most

common allergen was dichromate with 10 positive

results.

Conclusions: The results of this study confirm that

sunscreens are the more frequently involved substances

in photoallergic contact dermatitis in our population.

Identification of the photoallergen is the key element

for adequate disease control and patient education.

Key words: contact; dermatitis; photoallergic; sunsc-

reens.

Photoallergic contact dermatitis is a type IV hy-

persensitivity reaction to antigens and sunlight

on exposed areas. This reaction is the result of topical

or systemic exposure to different photosensitizers such

as drugs (topical antibiotics, systemic antibiotics,

NSAID), fragrances, sunscreens and plants, among

others (1, 2). The diagnostic and investigative tool is

photopatch test, in which a sensitized person is ex-

posed to an incriminated agent followed by exposure

to an appropriate irradiation (3).

Photodermatology groups such as the Scandinavian

(4), British (5), German, Austrian, Swiss (6, 7) and

others (3, 8, 9), have established standard series of

photopatch tests that include the most common

photoallergens responsible for these reactions in

each population. The spectrum of photoallergens

Photodermatol Photoimmunol Photomed 2006; 22: 189–192Blackwell Munksgaard

r 2006 The Authors.Journal compilationr 2006 Blackwell Munksgaard

189

varies in the different countries depending on the

substances (soaps, creams, sunscreens, among others)

available in the market and used daily. Therefore, a

unique series of allergens is not applicable to all

populations.

The photopatch tests have not been wholly stan-

dardized. Worldwide surveys have demonstrated that

the procedure varies from country to country and, in a

country, from one center to another. There are meth-

odological variations in the selection of substances,

their concentrations and vehicles used, the irradiation

sources, the programmed time for the application of

the substances, the irradiation sites and the reading of

the reactions. There is agreement only on the use of

ultraviolet A (UVA) and the application of the aller-

gens in duplicate, one site of which is irradiated and

the other used as a control area (4, 6).

The purpose of this study was to identify the

allergens responsible for photoallergic contact derma-

titis in patients evaluated in Bogota, Colombia. The

data could then be used to standardize photopatch

tests in this population.

Materials and methodsFrom the patients who attended Centro Dermatolo-

gico Federico Lleras Acosta between August 200l and

May 2003, we selected 82 patients who presented an

eczematous reaction in exposed areas suggestive of

photoallergic contact dermatitis, who did not have

history or clinical signs of solar urticaria, porphyria

or systemic lupus erythematosus and accepted to

participate in the study. Pregnant women were ex-

cluded. Photopatch tests were performed to this group

of patients with the standard series of sunscreens

(Chemotechnique Diagnostics, Vellinge, Sweden), 6-

methylcoumarin, dichromate and some of the more

frequent components found in the substances of daily

use in our population (moisturizing creams, cleansing

products, shampoos) (Table 1).

In order to identify the most common components

of these substances used daily by our patients, a

previous work was made listing all the components

of these products. It was found that the substances

contained in these products that have been reported as

photoallergens were the fragrances and the ultraviolet

filters (benzophenone-3, octylmethoxycinnamate), and

that most of the components of the analyzed products

have been reported in the literature as allergens but

not as photoallergens. In the present work we decided

to evaluate if some of these components could also

work as photoallergens in our population or could

simulate a clinical picture of photocontact allergy.

The group of allergens was applied in duplicate on

the healthy skin of the back of each patient and

covered with opaque tape. Twenty-four hours later

the tape was removed and the panel on the right was

irradiated with an UVA dose of 5 J/cm2, using a UVA

cabinet from Daavlin (Bryon, OH, USA), with an

irradiance of 10.4mW/cm2 which provided a 320–

400 nm spectrum. All the patients received the same

UVA dose and we did not cover again the panels with

opaque tape after the irradiation. The sides were

evaluated 24 h after the application of the allergens

and 24 and 72 h after irradiation. A trained dermatol-

ogist performed these readings.

The reactions were assessed according to the visual

scoring system recommended by the International

Contact Dermatitis Research Group and the patterns

described by Newman et al. (10). The reactions inter-

preted as photoallergic were those found positive only

in the irradiated panel, showing a crescendo pattern

(the reaction being more intense at the second reading

after the irradiation). Those which were positive in the

non-irradiated panel, or in both panels, were consid-

ered cases of contact allergy.

ResultsA total of 82 patients diagnosed with photoallergic

contact dermatitis were included in this study; 63%

were women and 37% were men. The average age at

the time of the outpatient visit was 40 years (range 7–

84 years). None of the patients showed a photosensi-

tive response to 5 J/cm2 of UVA.

Table 1. Allergens for photopatch testing

4-Tertbutyl-40methoxy-dibenzoylmethane (parsol 1789)

4-Aminobenzoic acid (PABA)

Homosalate

3–4-Methylbenzylidencamphor (eusolex 6300)

2-Ethylhexyl-4-dimethylaminobenzoate

(escalol 507, octyl dimethyl PABA)

2-Hydroxy-4-methoxybenzophenone (oxybenzone, benzophenone 3)

2-Ethylhexyl-4-methoxycinnamate (octylmethoxycinnamate,

parsol MCX)

2-Hydroxy-methoximethylbenzophenone (mexenone)

2-Phenylbenzimidazole-5-sulphonic acid (eusolex 232)

2-Hydroxy-4-methoxybenzophenone-5 sulphonic acid

(sulisobenzone, benzophenone4)

6-methylcoumarin

Cetyl alcohol

Phenoxyethanol

Methylparaben

Propylenglycol

Triethanolamine

Propylparaben

Trichlorocarbanilide

Dichromate

190

Rodrıguez et al.

Photopatch testsTwenty six of the 82 patients (31.7%) showed positive

results to one or several photoallergens, 25 patients to

ultraviolet filters (30.5%). Four of the 26 patients

showed positive photopatch tests responses to two

components, and four patients to three components of

the set of photoallergens tested (Table 2). A total of 38

positive photopatch test reactions were observed, 37

of these reactions were to ultraviolet filters. The most

common ultraviolet filter photoallergen was benzo-

phenone-3 with 22/82 positive results (26.8%), fol-

lowed by octyl methoxycinnamate 8/82 (9.7%),

benzophenone-4 and mexenone 2/82 (2.4%), phenyl-

benzimidazole sulphonic acid, methylbenziliden cam-

phor and octyl dimethyl PABA 1/82 (1.2%). One

patient showed a photoallergic response to 6-methyl-

coumarin.

A plateau pattern compatible with prolonged

phototoxicity reactions was observed in two patients.

These patterns were observed with 6-methylcoumarin

and butyl methoxydibenzoylmethane.

16/82 patients (19.5%) showed positive results to

one or several allergens both in the irradiated and

unirradiated control sites. Ten of these 16 patients

(62.5%) showed positive tests to dichromate. Five

showed a positive contact reaction to ultraviolet filters

(Table 3).

Three patients showed positive contact and photo-

contact responses to different allergens. One patient

showed a positive photocontact response to 6-methyl-

coumarin and a positive contact reaction to cetyl

alcohol and 3–4 methylbenzylidencamphor, another

patient showed a positive photocontact response to 2-

hydroxy-4-methoxybenzophenone and a positive con-

tact reaction to dichromate and the last one a positive

photocontact response to 2-hydroxy-4-methoxyben-

zophenone and a positive contact response to 2-

ethylhexyl-4-dimethylaminobenzoate.

Photopatch test relevanceRelevance of the positive results was evaluated taking

into account the patient’s use of any product con-

tained in the evaluated compound. It was found that

in 65.3% of the patients with positive results there was

a concordance between the photoallergen responsible

for the positive response and the use of different

substances such as creams, soaps, shampoos and

sunscreens containing such allergen.

No adverse reactions to the test were found.

DiscussionPhotoallergic contact reactions are considered a spe-

cial type of cell-mediated hypersensitivity for which

radiating energy is required to produce a photoanti-

gen, and induce an immunologic response. Endogen

as well as exogen substances can be transformed into

antigens by non-ionizing radiations (11).

Photopatch tests were positive in 31.7% of the 82

patients studied, in contrast to those findings reported

in the literature where test positivity varies from 4% to

11% with similar doses of irradiation, reading pat-

terns and interpretation, and groups of photoallergens

(sunscreens series) (3–6, 8). But in other studies, the

range of positivity varies from 19% to 38% (9, 12, 13).

In some of the previous studies photopatch tests

were performed as part of the complete evaluation of

patients with photosensitivity, without diagnostic spe-

cificity regarding photoallergic contact dermatitis (3,

4). The fact that we included only patients with this

clinical diagnosis could explain why we found a higher

Table 2. Photocontact allergic reactions

Number of

patients Photoallergen

1 3-(4-methylbenzyliden)camphor

2-hydroxy-4-methoxybenzophenone

2-hydroxy-4-methoxybenzophenone-5 sulphonic acid

1 2-ethylhexyl-4-dimethylaminobenzoate

2-hydroxy-4-methoxybenzophenone

2-ethylhexyl-4-methoxycinnamate

1 2-hydroxy-4-methoxybenzophenone

2-ethylhexyl-4-methoxycinnamate

2-hydroxy-methoxymethylbenzophenone

1 2-hydroxy-4-methoxybenzophenone

2-ethylhexyl-4-methoxycinnamate

2-phenylbenzimidazole-5-sulphonic acid

1 2-ethylhexyl-4-methoxycinnamate

2-hydroxy-methoxymethylbenzophenone

2 2-hydroxy-4-methoxybenzophenone

2-ethylhexyl-4-methoxycinnamate

1 2-hydroxy-4-methoxybenzophenone

2-hydroxy-4-methoxybenzophenone-5-sulphonic acid

15 2-hydroxy-4-methoxybenzophenone

2 2-ethylhexyl-4-methoxycinnamate

1 6-methylcoumarine

Table 3. Contact allergic reactions

Number of

patients Allergen

1 3-(4-methylbenzilyden)camphor

Cetyl alcohol

1 2-hydroxy-4methoxybenzophenone-5-sulphonic acid

Dichromate

Dichromate

2 2-hydroxy-4-methoxybenzophenone

1 2-ethylhexyl-4-dimethylaminobenzoate

1 Triethanolamine

1 Propylparaben

191

Causal agents of photoallergic contact dermatitis

rate of positive photoallergic reactions. In one study,

the photopatch tests were applied specifically to pa-

tients with clinical histories suggestive of photoallergic

contact dermatitis resulting in 19% of positive photo-

patch test reactions (9).

UV filters were the more frequently photoallergens

(30.5%) responsible for positive photopatch test re-

sults in the 82 patients tested, this finding is concor-

dant with the literature (3, 4, 14, 15). Similar to other

studies, benzophenone-3 was the most common

photoallergen responsible for positive reactions

(26.8%) (3–6, 8). Next on the list was octylmethox-

ycinnamate with 9.7% in contrast to other studies that

found a lower percentage (3–4%) (9, 16). The high

percentage of reactivity found with these ultraviolet

filters in this study was associated with the common

use of them in sunscreens and also with the frequent

use of substances containing it such as emulsifying

creams and shampoos.

The following photoallergens: methylbenzyliden

camphor, octyl dimethyl PABA, mexenone, benzo-

phenone-4 and phenylbenzylimidazole sulphonic acid,

also presented positive responses although in a lower

percentage (2–5%); similar results (2–4%) are found

in the literature (6, 9, 16).

6-methylcoumarin has been included as photoaller-

gen in some cases in the literature (6, 17). In this study,

it was found as causing photocontact allergy in one

patient.

In 65.3% of the cases, there was concordance

between the positive results to different photoallergens

and the use of products containing them. Some studies

evaluate this aspect and found 11–20% of clinically

relevant positive test responses, given by positive

results to fragrances such as musk ambrette and 6-

methylcoumarine (8, 2, 13). 19.5% of the 82 patients

showed contact allergy responses to one or several

allergens. These cases were erroneously diagnosed as

photoallergic contact dermatitis, 62.5% of them cor-

responded to dichromate. It is important to note that

dichromate can produce a similar clinical picture,

acting as an aeroallergen (18, 19).

Our results confirm that UV filters are the more

frequently involved substances in the photoallergic

reactions in our population. The rate of positivity of

the photopatch tests could be increased if only pa-

tients with clinical diagnosis of photoallergic contact

dermatitis are photopatch tested. In our population

dichromate should be included in the photopatch

series considering that photoallergic contact dermati-

tis and air-borne contact dermatitis could be clinically

similar.

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Accepted for publication 11 January 2006

Corresponding author:

Martha Cecilia Valbuena

Avda. 1 No. 13a-61

Bogota

Colombia

Tel: 157-1-2428160

Fax: 57-1-3373597

e-mail: mvalbuen@cable.net.co

192

Rodrıguez et al.