ABSTRACT
As phototoxic skin reactions caused by psoralen are induced by wavelengths within the UVA1 spectrum, we assessed the potential of the small amount of psoralen in a normal diet to provoke phototoxicity in volunteers with skin types I and II. Threshold erythema was unaffected by ingestion of a 200-g portion of parsnip.
Subject(s)
Diet , Erythema/chemically induced , Furocoumarins/adverse effects , Photosensitivity Disorders/chemically induced , Radiation-Sensitizing Agents/adverse effects , Ultraviolet Rays/adverse effects , Adult , Aged , Apium/adverse effects , Apium/chemistry , Erythema/etiology , Female , Food Handling , Furocoumarins/analysis , Hot Temperature , Humans , Male , Methoxsalen/adverse effects , Methoxsalen/analysis , Middle Aged , Pastinaca/adverse effects , Pastinaca/chemistry , Photosensitivity Disorders/etiology , Plant Epidermis/adverse effects , Plant Epidermis/chemistry , Radiation-Sensitizing Agents/analysis , Skin/drug effects , Skin/radiation effects , Ultraviolet Therapy/adverse effectsABSTRACT
OBJECTIVE: To determine the time course and dose-response characteristics of UV-A1 erythema in the Tayside region of Scotland. DESIGN: Adult volunteers (skin types I and II [n = 13] and III and IV [n = 11]) were exposed to geometric dose series of UV-A1 irradiation from a high-output source on photoprotected lower back and inner forearm skin. SETTING: Photobiology unit in a university hospital. MAIN OUTCOME MEASURES: The minimal erythema dose (MED) was recorded visually and erythema was assessed objectively by erythema meter at 4, 8, 24, and 48 hours after exposure. RESULTS: Peak erythema (lowest visual MED) was seen at 8 hours on the back and arm in 11 subjects with skin types I and II and on the back at 8 hours in 9 subjects and on the arm at 4 hours in 10 subjects with skin types III and IV. The lowest median (range) MED was 20 J/cm(2) (14-56 J/cm(2)) on the back and 42 J/cm(2) (20 to >80 J/cm(2)) on the arm at 8 hours for subjects with skin types I and II and 28 J/cm(2) (20-112 J/cm(2)) at 8 hours on the back and 56 J/cm(2) (28-80 J/cm(2)) at 4 hours on the arm for subjects with skin types III and IV. The D(0.025), an objective measure that corresponds approximately to the visual MED, demonstrated a broad peak from 8 to 24 hours. CONCLUSIONS: Our local population is more erythemally sensitive to UV-A1 radiation than reports suggest. Daily dose regimens may risk cumulative erythema. Lower starting doses should be used in this population. The wide range of MEDs highlights the need for MED testing.
Subject(s)
Erythema/etiology , Skin Pigmentation , Ultraviolet Rays/adverse effects , Adult , Arm , Back , Dose-Response Relationship, Radiation , Hospitals, University , Humans , Middle Aged , Scotland , Time FactorsABSTRACT
BACKGROUND: As little has been published on the course of idiopathic solar urticaria (SU) patients cannot receive comprehensive prognostic advice. OBJECTIVE: To determine the prognosis and photobiological characteristics of idiopathic SU. DESIGN: Historical cohort study, with inception cohort followed up from time of diagnosis. Follow-up for a median of 4 years (range, 3 months to 26 years) after diagnosis. SETTING: Tertiary referral center for the investigation of photodermatoses in Scotland. PATIENTS: The study included 87 patients, 61 (70%) of whom were female, with phototest-confirmed idiopathic SU between 1975 and 2000. Sixty patients (69%) were followed up clinically, and 25 patients (29%) were phototested on 2 or more occasions. INTERVENTIONS: Investigations at time of diagnosis included monochromator phototesting. Further monochromator phototesting was performed in those patients in whom it was clinically indicated (select subgroup), and all patients who could be traced received a follow-up questionnaire. MAIN OUTCOME MEASURES: Characteristics of SU, responsible wave bands, and prognosis for clinical resolution. RESULTS: The prevalence of idiopathic SU in Tayside, Scotland, is estimated to be 3.1 per 100 000. Action spectra were typically broad, with 63% reacting to more than 1 wave band, and the most common provoking wavelengths were the longer UV-A and the shorter visible ones. The majority of subjects were affected perennially (68%), by radiation transmitted through glass (83%) and thin clothing (76%). Coexistent polymorphic light eruption occurred in 20 patients (23%), and another photodermatosis occurred in 6 patients, 3 of whom had chronic actinic dermatitis. In those with SU alone, the mean age at onset was 41 years. The probability of clinical resolution at 5 and 10 years after diagnosis was 0.12 (95% confidence interval, 0.06-0.24) and 0.26 (95% confidence interval, 0.15-0.43), respectively. CONCLUSION: Idiopathic SU is a chronic disease. The majority of this cohort was still affected after 5 and 10 years.
