This is a randomized, single-center, controlled, within-subject comparison study assessing the sensitization potential of the investigational product, LEO 43204 gel under open conditions in healthy volunteers.

LEO 43204 Gel and Vehicle Gel will be applied to adjacent sites on the infrascapular area of the back. Evaluation of dermal reactions at the application sites will be assessed clinically using a visual scale that rates the degree of erythema, edema and other signs of cutaneous irritation.

Following induction, subjects will have a 10 to 14-day Rest Phase, after which they will enter the Challenge Phase, which consists of one 48-hour application to a naive site on the opposite side of the back. Observations at the naive site during Challenge and the patterns of reactivity during the Induction Phase will provide a basis for an interpretation of contact sensitization.

A total of 10 applications will be made over a period of approximately 6-8 weeks.

Inclusion Criteria:

1. Are free of any systemic or dermatologic disorder, which, in the opinion of the investigator, will interfere with the study results or increase the risk of adverse events;
2. Fitzpatrick skin types I-IV (due to lack of safety data for the investigational product in darker skin types);
3. Complete a Medical Screening form as well as a Medical Personal History form;

Exclusion Criteria:

1. Have any visible skin disease at the application site which, in the opinion of the investigative personnel, will interfere with the evaluation of the test site reaction;
2. Are not willing to refrain from using topical/systemic analgesics for 72 hours prior to and during the study (daily use of 81 mg aspirin is acceptable and occasional use of acetaminophen will be permitted);
3. Are using systemic/topical corticosteroids for 3 weeks prior to and during the study, or systemic/topical antihistamines for 72 hours prior to and during the study;
4. Are using medication which, in the opinion of the investigative personnel, will interfere with the study results, including anti-inflammatory medications;
5. Are unwilling or unable to refrain from the use of sunscreens, cosmetics, creams, ointments, lotions, or similar products on the back during the study;
6. Have psoriasis and/or active atopic dermatitis/eczema;
7. Have damaged skin in or around the test sites, including sunburn, excessively deep tans, uneven skin tones, tattoos, scars, excessive hair, numerous freckles, or other disfigurations of the test site;