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The appearance of this distribution of nevi in sun-protected children as early as age 6 is problematic for explanations based on differential sunlight exposure and hormonal changes at puberty.

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^The action spectra were determined with a high intensity light source on II patients (including 4 persistent light reactors) known to be photosensitive to bithionol and halogenated salicylanilides. Maximum photosensitivity observed on patch tests containing the sensitizer was in the range of 360 nm. but no reaction occurred above 420 nm. The persistent light reactors had a considerably lowered sunburn MED below 3.30 nm. compared with control groups. The absorption spectra of the sensitizers was determined in dimethyl formamide and in 95",, ethanol at various pH. The halogenated salicylanilides gave a maximum absorption at 282 nm. in an acid pH. but in a basic pH above 8. when phenolic ionization occurs, a second absorption peak at 360 nm. is found. Maximum fluorescence was achieved by excitation in the region of 360 nm. If the concentration of the sensitizer is equal (1%) then the order of decreasing photosensitizing ability of the tested substances was tetrachlorosalicylanilide (TCSA), bithionol. 4 ,5-dibromosalicylaniIide (DBS) and 3,4 ,5-tribromosalicylanillde (TBS). Guinea-pigs could be sensitized with TCSA within one week using combined long U.V. (320^20 nm.) and sunburn irradiation, but no sensitivity occurred with irradiation for 16 weeks using only long U.V. Patch tests on sensitized patients to photodecomposition products of TBS and DBS were negative. The possible mechanisms in the production of the persistent light reactors are discussed., halogeuated salicylanilides aud related compounds have been extensively used as antimicrobial agents by various manufacturers in soaps and cosmetics during thp last decade.An outbreak of contact photosensitivity to one of these compounds-3,3',4',5tetrachlorosalicylanilide (TCSA) was initially reported in England by Wilkinson (limia, b; I!)62a. b) by (Hainan et al. (lOHI) and by Crow (19fil). Wilk^inson (1962) domonsti-atod that in some Tt'SA stmsitive ^nitients, cross sensitivity to 3,4',5tribroniosalicylanilido (TIJ8) occurred. Epstein and Enta (li)65) reported patients sensitive to TBS in whom cross sensitivity to TCWA occurred. Jilison and Baughman (1963) and Baughman (1964) reported contact photodermatitis to a cream containing 2-hydroxy 3,5-diclilorox>henylsulphide (bithionol) and demonstrated cross photosensitivity with halogenated .salieylanilides and with hexachlorophane. Photosensitivity to 4',5-dibromosalicylanilide (DBS) was re])nrted by Malloy and Mayer (1966) and by Harber et al. (1906a, b) who also reported cross photosensitivity between the halogenated salicylanilides, e.g. with TCSA and with Accn])ted fur publkiatioii .liine 8th, 1969. • Pnwenti'd in part at thf Fifth International Congress of Photo biology, Hanover, Now Hampshire.