Topical
immunotherapy is widely used in the treatment of
alopecia areata (AA).
Alopecia areata incognita (AAI) is a relatively common disorder, predominantly affecting females, characterized by widespread hair thinning in the absence of typical alopecic patches. AAI can have a chronic relapsing course and in some cases can be resistant to current standard treatments. Topical
immunotherapy has been used in the management of AA with encouraging results, but to date there are no literature studies reporting the efficacy of topical
immunotherapy with
squaric acid dibutylester (
SADBE) in AAI. The aim of our study is to evaluate the efficacy and tolerance of topical
immunotherapy with
SADBE in AAI not responding to conventional
steroid therapy. A total of 12 patients were enrolled in our
Hair Disease Outpatient Service, with a proved histological diagnosis of AAI, and resistant to classical
steroid therapy. Each patient underwent global photography, pull test, and trichoscopy at beginning and during the follow-ups. The efficacy of topical
immunotherapy with
SADBE was assessed by evaluating the changes of clinical and trichoscopic signs. Complete regrowth was achieved in 66.7% of cases (8/12), three patients remained unchanged on clinical evaluation but showed subclinical improvement on trichoscopy, whereas one patient progressed and worsened both on clinical and trichoscopic examination. All patients reported scalp diffuse mild
erythema and
itching the day after the application of
SADBE, which were well tolerated. Three patients developed reactive cervical lymphoadenomegaly. No other side effects were observed. Topical
immunotherapy with
SADBE is widely used in the management of patchy AA and can be considered an effective alternative in resistant AAI, providing visible clinical and trichoscopic improvement in the majority of cases. Further studies are warranted to confirm and validate our findings.