Does the minimal phototoxic dose after 8‐methoxypsoralen baths correlate with the individual’s skin phototype?

Background/Aims: Up to now no data have been available concerning whether there is a significant correlation between skin phototypes and the minimum phototoxic dose (MPD) after bath water delivery of 8‐MOP.Methods: The skin phototype of each of 46 patients was determined based on the individual past history of solar‐induced burning and tanning. In addition, the MPD of each patient was assesed after photosensitization with a warm water bath (37 °C, 98.6 °F) containing 1.0 mg/l 8‐methoxypsoralen (8‐MOP). Statistical analysis was performed using a Mann‐Whitney U‐test and Spearman rank order correlation.Results: The median MPD in patients with skin phototype II was 2.0 J/cm2 (range ≤0.5 to ≥3.5) versus 1.5 J/cm2 (range 1.0 to ≥3.5) in patients with skin phototype III. There was a considerable overlap between both groups. No significant difference was detected comparing both groups (P=0.7326) and Spearman rank order correlation revealed no correlation between skin phototype and MPD.Conclusion: Erythemal sensitivity in PUVA bath therapy, measured as MPD, is not correlated with sun‐reactive skin phototype in skin types II and III. Thus skin phototype is not a suitable indicator for the initial UVA dose in PUVA bath photochemotherapy.