Inclusion Criteria:

• Male or female voluntary patients at least 18 years old
• For female patients with child-bearing potential, negative pregnancy test at baseline
• Patients with a clinical and photobiological diagnosis of idiopathic SU
• Patients with no underlying condition, or with underlying conditions provided that these conditions are stable and under control
• Patients able to follow instructions
• Written informed consent from the patients

Exclusion Criteria:

• Children (less than 18 years old)
• Pregnant or lactating women
• Women with a positive pregnancy test at baseline
• Patients with spontaneous occurrence of SU lesions on the back within 3 days prior to study entry
• Patients with a known allergy to one of the ingredients contained in the test products
• Patients who have applied EP to back skin over the previous 2 weeks before study entry
• Patients who have applied topical corticosteroids to back skin within 7 days prior to study entry
• Patients who have applied an emollient including white soft paraffin on back skin within 2 days prior to study entry
• Patients with systemic exposure to corticosteroids, anti-inflammatories or other immunosuppressive agents within the last 4 weeks prior to study entry
• Patients with oral antihistamines within the last 2 days prior to study entry
• Patients who have been administered systemic or topical photoactive medications for phototherapy or phototherapy alone within 1 week prior to study entry
• Patients with an unstable or non-controlled underlying condition
• Patients who are not able to follow instructions
• Patients who have participated in a study within the 3 months prior to study entry
• Patients who refuse to give written informed consent