Physiological Variation in the Erythemal Response to Ultraviolet Radiation and Photoadaptation

Abstract

We have studied the cutaneous response to ultraviolet radiation, measured objectively as erythema in a sample of 12 body sites on 15 Northern European subjects with multiple doses of ultraviolet B (UVB). Skin pigmentation and the development of photoadaptation in response to five repeated doses of irradiation at three body sites was also measured. We report striking differences of up to 5-fold at different body sites to the same challenge dose (p < 0.001) and demonstrate that for this population, site variation is just as important as between-person variation. Skin color at each body site is a strong predictor of response (p < 0.001) and that this cannot be attributed to vascular differences, but instead we believe it reflects site-specific variations in melanin pigmentation. We also observed similar but smaller within-person effects for responses to another inflammatory agent, dithranol (p < 0.01). Despite this, we did not find evidence for differences in the development of photoadaptation by body site. These results have clear clinical implications for the practice of phototesting prior to commencing phototherapy, for therapeutic failure in sites such as the legs in patients with psoriasis, and perhaps for melanoma body-site distribution.

Tacrolimus ointment neither blocks ultraviolet B nor affects expression of thymine dimers and p53 in human skin

“…On two previously marked adjacent sites, we evenly applied by means of a rubber glove 2 mg/cm 2 tacrolimus ointment and 2 mg/cm 2 vehicle thrice daily over a 3-day period (9 applications in total). In order to minimize anatomically dependent variations of UV sensitivity, the interventions and measurements were carried out at the same horizontal level (medial scapular region) [14]. All test substances were administered in a non-blinded manner according to a fixed plan.…”

Knowledge of Body Site Variability in Ultraviolet-Induced Erythemal Responses Guides Choice of Site for Pre-Therapy Minimal Erythema Dose Testing

“…To the Editor: Waterston et al (2004) have confirmed that there is marked variability between body sites in ultraviolet-induced erythemal responses. Although there are differences in erythemal responses to different ultraviolet wavebands (Olson et al, 1966), their findings are in line with those of the earlier studies in which unfiltered mercury arc lamps (Schall and Alius, 1926;Wucherpfennig, 1931) and a xenon arc monochromator delivering different wavebands (Olson et al, 1966) were used.…”

“…The primary purpose of pre-treatment MED testing is to determine a starting dose that will not cause uncomfortable (or more serious) erythema. Waterston et al (2004) found (as shown in their Fig 3) that if a whole-body starting dose of 50% MED (upper back, 24 h reading) was selected for their 15 study volunteers not one would have received a dose greater than the MED on any tested body site. If a 70% upper-back MED starting dose was used only four subjects would have received a dose slightly above the MED on the chest or lower back.…”

“…The trunk appears to be the site most sensitive to erythema (Johnson et al, 1968). This is true whether the erythemal response is assessed as degree of erythema 7 h following a measured ultraviolet dose (Schall and Alius, 1926), as the dose producing minimal erythema detectable by the human eye (minimal erythemal dose (MED)) 8 h after administering a series of doses (Olson et al, 1966), or assessed in both these ways 24 h after irradiation with a broad-band fluorescent ultraviolet B lamp (Waterston et al, 2004).…”

In Locus Minoris Resistentiae—Or Not?

“…In this issue of the journal, Waterston et al (2004) studied the cutaneous response to ultraviolet B (UVB) radiation in normal human subjects of Fitzpatrick phototypes I and II by first measuring erythema responses at multiple anatomical sites. They administered a series of incremental doses of energy between 38 and 300 mJ per cm 2 at 12 pairs of body sites.…”