Download Photoallergic dermatitis and Photopatch testing

Photocontact dermatitis and
Photopatch testing
Photoinduced skin disease
• Autoimmune disease eg. lupus
• Metabolic conditions eg porphyria
• Internal or external exposure to photoactive
agents
• Others eg.
Polymorphic light eruption
Chronic actinic dermatitis
Mechanism of skin disease due to
internal or external agents
• Phototoxic
• Photoallergic
-Some agents can cause both phototoxic and
photoallergic reactions
Phototoxic Reaction
• Can occur from first contact
• Previous sensitivity not required
• Could occur in anyone under certain
conditions ie. Sufficient dose/ UV intensity
eg. psoralen exposure, porphyrins, drugs
(amiodarone, tetracyclines)
Photoallergic reaction
• T cell mediated disease.
• Requires someone to be sensitised ie. not on first
exposure
• Usually develops 24 to 72 hours after irradiation
• Lower concentrations needed
• Requires exposure to agent plus UV exposure
• Radiant energy causes modifications within the agent
to result in a photo-antigen.
• Wavelength of radiation to induce reaction depends on
chemical structure of allergen
• Diagnosed by photo patch tests
Mechanism of a Phototoxic Reaction
Photosensitiser and Radiation (UV)
Absorption of Energy
Elevation of Molecules to an excited State
Photodynamic or non photodynamic reaction
Damage to Cell components
Inflammation
Mechanism of a Photoallergic Reaction
Photoallergen and radiation (UV)
Absorption of Energy
Elevation of Molecules to an Excited State or binding
Generation of a Photoallergen
Formation of a Complete Antigen
Inflammation by a T cell mediated Immune Response
Clinical presentation of Photo induced
disease
• “Exposure” Pattern distribution
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V of neck
Back of hands
Extensor surface of forearms
Sharp cut off for clothing
Sparing of photoprotected areas (under chin and
behind ears)
• Phototoxic : often resembles sunburn. Limited to
exposed areas. Can be bullous/ eczematous
Indications for Photopatch testing
• Eczematous eruption affecting mainly light
exposed sites
• Worsening of condition with sun exposure
• History of reactions to sunscreens
• Suspicion of photoallergic drug eruption
Photopatch test Method
• Patient seen at day 0
• Patch tests allergens applied to back in
duplicate one set either side of spine
• Use a photopatch test series and also add
patient’s own products
• Other patch tests may be applied as necessary
When is the best time to irradiate the
skin?
• 3 different protocols have been described one
of which involves exposure to UV at 24 hours
• Retrospective study done in Leeds (Contact
Dermatitis 2006). Three sets of allergens
applied. Patients had irradiation at 24 hours to
one set and 48 hours to another. 48 hours
exposure was more sensitive at picking up
allergens
UV Dose in cases of photosensitivity
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Light source 315-400 nm ie UVA range
Eg PUVA Waldmann 800 canopy
In most cases 5J/cm2
This would not normally induce erythema
If strong suspicion of photosensitivity disorder
ideally check MED to UVA initially
• Test at 50% MED
Day 2
• Patient seen for day 2 read
• Patches removed and first reading performed
• One set (set B) covered with UV protective
material
• Set A left exposed
• UV source- usually UVA flat bed
• Dose usually 5J/cm2 at a distance of 15 cm
from the back
Day 4
• Results read at day 4
• Interpretation of results
• “Crescendo” phenomenon –increasing
reaction from 48 hours to 96 hours post
exposure - seen in photoallergic
• “decrescendo”- reducing/ clearing reaction
– Seen in phototoxic
SCENARIO 1
Positive result in set A and set B. Both reactions of similar
intensity
 normal allergic contact reaction
SCENARIO 2
Positive result in set A and set B. Reaction in set A of
greater intensity
allergic contact reaction with combined photo contact
allergy
SCENARIO 3
Negative result in set B. Positive reaction in set A.
 photoallergy
SCENARIO 4
Both set A and set B negative
SCENARIO 5
General erythema on exposed area
May need to see the patient again on day 7 if
nature of allergy not clear
What Allergens are Important?
• Photoallergic Contact dermatitis is becoming less
common
• Many common allergens have been withdrawnparticularly fragrance ingredients eg musk
ambrette and 6 methyl coumarin- banned by the
international fragrance association
• Also halogenated salicylanilide and chlorinated
phenols previously commonly used antiseptics
Sunscreens
• Increasing use in cosmetics
• All agents that absorb UV light can cause
contact dermatitis
• Eg. Cinnamates, benzophenones, oxybenzones
and dibenzoyl methanes
• Reflectant sunscreens are not photosensitisers
UK Multicentre study BJD 2006
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Bryden et al
1155 patients
130 (11.3%) allergic reaction
51 (4.4%) photo contact allergic reaction
64 (5.5%) Contact allergy
15 (1.3%) both contact allergy and photo
contact allergy
Photopatch Testing of 182 Patients: A 6-Year Experience at the
Mayo Clinic
Scalf et al Dermatitis 2009;20:44-52
Retrospective study. 54 patients (29.7%) photoallergic contact reactions and 29
(15.9%) had allergic contact reactions to the photoallergy series
Commonest allergens seen were topically applied medications, sunscreen agents
(benzophenone 4), fragrances (sandalwood) and antispetics
Photopatch Testing: The 12 year experience of the German, Austrian and
Swiss photopatch test group JAAD 2000
1129 patients from 1985-1990
2859 positive reactions: 28.6% were contact allergy
3.8% classified as photoallergic
1261 patients from 1991-1997 had 1415 reactions
28.7% felt to be contact allergy, 8.1% photoallergic
Common reactions seen were topical NSAIDs, disinfectants and phenothiazine
What allergens should we test?
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Sunscreen chemicals
Fragrance ingredients
Drugs
Miscellaneous chemicals
Local phototesting series
• Sunscreens
• Drugs (ketoprofen, etofenamate, piroxicam,
benzydamine, promethazine, ibuprofen,
diclofenac)
Patient Counselling
• Explain allergens exposure, avoidance
• Written information sheets
• Advice on suitable alternatives
Conclusion
• Photopatch testing is time consuming and
specialised
• Uncommon but very important to those
affected
• Mostly due to sunscreens