Photoallergy
Outline: Photoallergy
Objective: To assess the photoallergic contact sensitization potential of 1-4 test articles on human subjects (using a modification* of the Photomaximization Test described by Kaidbey and Kligman, Contact Dermatitis 6: 161-169, 1980).
Subjects: 25 healthy men and women
Timing: 6-week test
Start test within2 weeks of receipt of samples
Report issued within 3 weeks of study completion
Quantity: 8 oz.

Methodology:
Clinical assessment of dermal response by a trained evaluator
Light Source: UV-A: A bank of four (4) 40W fluorescent bulbs (F40/350BL) with a continuous long-wave UV-A spectrum ranging between 320 and 400 nm (peak 365nm) is used. Exposure intensity is measured at a distance of 10 cm from the lamps using a long wave UV meter (Model J-221, Ultra-Violet Products, Inc., San Gabriel, CA). Dosage of irradiation is calculated as follows: Intensity (mW/cm2) x Time (minutes) x 60 seconds x .001 =Dosage (J/cm2).

Procedures:
The volar surfaces of both forearms are alternately designated as either the irradiated test arm or the non-irradiated control arm as test subjects are empaneled. The non-irradiated arm serves to exclude possible non-UVA-dependent dermal reactivity.

Induction Phase
Approximately 0.2 mL or grams of each test article is applied to test sites on each forearm using occlusive patches. Semi-occlusive patches may be used when evaluating known irritating and/or volatile materials.

Twenty-four hours later the patches are removed at the clinic, both test and control sites are scored for dermal reactivity and the UVA-designated sites irradiated with 4-5 Joules of UVA. Fresh patches are reapplied to the same test sites. During Week 1 this procedure is repeated daily (Tuesday-Friday) until 5 patch applications and 4 irradiation exposures to the UVA-designated arm are completed. Patches applied on Friday are left in place until Monday when the irradiation/reapplication procedure is again repeated for a second week. During Week 2, patches applied on Thursday are removed and scored on Friday. This 2-week procedure results in a total of 9 induction patch applications and 8 induction irradiations.

If a subject develops a level 2 reaction or greater during the Induction phase, the patch is applied to an adjacent fresh site for the next application. If a 2 or greater reaction occurs on the new site, no further induction applications are made. However, any reactive subjects will be subsequently patched/irradiated with the test article on virgin test sites during the Challenge phase of the study.

Challenge Phase
After an approximate 2-week Rest phase, fresh challenge patches are applied to virgin test sites adjacent to the original irradiated and non-irradiated test sites. Twenty-four hours later, the patches are removed from the UVA-designated test area. The sites are gently wiped, examined for any dermal reactivity and irradiated with the same UVA dosage as the Induction phase. Following irradiation of the UVA-designated test site, the control (non-irradiated) patches are removed, the sites gently wiped and examined for dermal reactivity. The irradiated and non-irradiated control sites are again scored, 24 and 72 hours after irradiation. The test subjects are asked to report any delayed reactions that might occur after the final challenge patch readings.


Skin Scoring Criteria
Skin responses are scored according to the following 6-point scale:
0 = (None) No evidence of any effect.
+ = (Barely perceptible) Minimal, faint, uniform or spotty erythema or tanning.
1 = (Mild) Pink, uniform erythema or tanning covering most of the contact site.
2 = (Moderate) Pink-red erythema or tanning, uniform in the entire contact site.
3 = (Marked) Bright red erythema or tanning with/without petechiae or papules.
4 = (Severe) Deep red erythema with/without vesiculation and/or weeping or dark tanning.

Accompanying edema (swelling) or other possible dermal sequelae are appropriately recorded and described as mild, moderate or severe.

*Nine induction patches and 8 irradiations are made over a 2-week Induction phase. There are no "rest" periods between induction patches.