Optimal microneedle length for hair regrowth in hair cycle arrest (alopecia X) in six dogs.

Background: Hair cycle arrest (HCA) is a chronic alopecic disorder in dogs. Clinical responses vary and are often insufficient. Microneedling (MN) has been used as a successful treatment for HCA in dogs; ideal protocols have not yet been established.

Objectives: The objective of the study was to compare the efficacy and safety of three needle lengths for MN in dogs with HCA.

Animals: Six unrelated client-owned dogs, including five Pomeranians and one mixed-breed dog, diagnosed with HCA.

Materials and methods: Individual alopecic sites were divided into three sections. For each section, different lengths of needles (1, 2 and 3 mm) were used. Efficacy and safety were evaluated at 1, 3 and 6 months. Treated sections were monitored for 20 months.

Results: Three months after treatment with 3 mm needles, all sections showed hair regrowth. There was no hair regrowth in two of six sections treated with 2 mm needles, and four of six sections did not show a response to treatment with 1 mm needles. Two dogs developed transient pruritus. Five of six dogs had recurrent hair loss between 5 and 16 months of follow-up.

Conclusion and clinical relevance: Microneedling using longer needles stimulated better hair regrowth in dogs with HCA. Alopecia relapsed in most dogs and minor pruritus occurred in some dogs.