Angioedema After Squaric Acid Treatment in a 6-Year-Old Girl.

Alopecia areata (AA) involves the immune-related destruction of hair follicles, resulting in patches of complete hair loss, most often on the scalp. The topical sensitizer squaric acid dibutylester (SADBE) is a popular treatment option given its low side-effect profile, hair regrowth potential, and lack of cross-reactivity with other chemicals. We describe a unique case of a 6-year-old girl who developed angioedema after SADBE treatment for AA.