Background: Among contact allergens that are frequently used in the treatment of alopecia areata (AA), squaric acid dibutylester (SADBE) stands out for its good tolerability and its mild side effects.
Methods: One hundred and forty-four patients with AA of varying degrees were treated with SADBE. Of these, 71 had AA affecting less than 50% of the scalp, and 73 had a severe form, including 13 patients with alopecia totalis (AT) and two with alopecia universalis (AU). The patients were treated using both traditional and nontraditional methods.
Results: In the less severe form, we obtained a 80% rate of regrowth, compared to the 49% of the more severe form including 13 cases of AT and the two of AU. The failure rate was higher for patients with the more severe form (29%) compared to a 7% rate only for patients with mild AA. We also observed four cases of initial regrowth on the side of the scalp opposite to the site of application ('castling phenomenon'). Among those patients who were treated with application of SADBE on the right side of the back, three displayed regrowth on the left side of the scalp, (i.e., on the opposite side) and in an area distant from the site of application; for two patients the regrowth began on the right side of the scalp and one of them also displayed growth of fine hairs in the right dorsal region, the site of application of the compound.
Conclusions: Our data further support the hypothesis of a systemic action of SADBE; however, further confirmation on a larger sample of cases is needed.