Photodegradation of Dibenzoylmethanes: Potential Cause of Photocontact Allergy to Sunscreens
Artikel i vetenskaplig tidskrift, 2009

One of the most frequently observed photoallergens today is the sunscreen agent 4-tert-butyl-4′-methoxy dibenzoylmethane (1a). The structurally similar compound, 4-isopropyldibenzoylmethane (1b), was a common cause of sunscreen allergy in the eighties and early nineties but was removed from the market in 1993 and replaced with dibenzoylmethane 1a. We have studied the photodegradation of the dibenzoylmethane 1a, to better understand how these substances cause an immune reaction. Several expected degradation products were formed and identified. Of these, arylglyoxals and benzils were of particular interest because they were unexplored as potential contact allergens. The allergenic potential of photodegraded 1a was evaluated by screening the formed arylglyoxals and benzils for their sensitizing capacity in the murine local lymph node assay. The arylglyoxals were found to be strong sensitizers. They were also found to be highly reactive toward the nucleophile arginine, which indicates that the immunogenic hapten-protein complex could be formed via an electrophilic-nucleophilic pathway. By varying the electron-withdrawing or -donating capacity of the substituent in the para position of the arylglyoxal, the electronic effects were shown to have no significant impact on either the sensitizing or the electrophilic power of arylglyoxals. Thus, a change in the substitution pattern of the parent dibenzoylmethane will not influence the sensitizing capacity of the products formed from them upon photodegradation. Furthermore, the combined studies of benzils, using the local lymph node assay and a cell proliferation assay, indicate that the benzils are cytotoxic rather than allergenic. Taken together, this study presents strong indication that photocontact allergy to dibenzoylmethanes is caused by the arylglyoxals that are formed upon photodegradation.


photocontact allergy


local lymph node assay






I. Karlsson

Göteborgs universitet

Lisa Hillerström

Göteborgs universitet

Anna-Lena Stenfeldt

Göteborgs universitet

Jerker Mårtensson

Chalmers, Kemi- och bioteknik, Organisk kemi

Anna Börje

Göteborgs universitet

Chemical Research in Toxicology

0893-228X (ISSN) 1520-5010 (eISSN)

Vol. 22 1881-1892


Dermatologi och venereologi

Analytisk kemi

Annan medicinsk grundvetenskap


Mikrobiologi inom det medicinska området

Organisk kemi