The Effect of Local Skin Precooling on Alleviating Injection Site Pain in Patients With Androgenetic Alopecia Receiving a Scalp Nerve Block

BACKGROUND: Scalp platelet-rich plasma (PRP) mesotherapy is commonly used to increase hair density and improve scalp health in patients with androgenetic alopecia. While PRP therapy is favored for its lower risk of adverse effects and reduced treatment frequency compared to other methods, the potential for injection site pain remains a significant challenge, potentially reducing patient compliance and treatment continuation. OBJECTIVE: To evaluate the effectiveness of local skin precooling in reducing injection site pain during scalp PRP mesotherapy in patients with androgenetic alopecia. STUDY DESIGN: A single-center retrospective study. SETTING: This study was conducted at the Precision Health Management Center of the Shanghai East Hospital, Tongji University School of Medicine, People's Republic of China. METHODS: Data were collected from 100 patients (82 men, 18 women) aged 18-50 years who underwent scalp PRP mesotherapy from August 2020 through July 2024. Patients were divided into 2 groups: Group A (n = 50) received local skin precooling administered using sterile gloves by way of soft ice packs for 2 minutes pre scalp nerve block; Group B (n = 50) did not receive local skin precooling pre scalp nerve block. All patients received scalp PRP mesotherapy. Pain perception was measured using a 100-mm Visual Analog Scale (VAS) at multiple time points: 30 seconds post scalp nerve block at 2 nerve points, at immediate posttreatment, and at one- and 24-hours posttreatment. Demographic data and Positive and Negative Affect Schedule scores were also collected. Safety outcomes included the incidence of adverse events. RESULTS: VAS scores were significantly lower in Group A compared to Group B at all measured time points. At 30 seconds post scalp nerve block, Group A showed a 34.08% pain reduction at the supraorbital nerve and the supratrochlear nerve and an 18.86% pain reduction at the greater occipital nerve compared to Group B. VAS scores for Group A at immediate posttreatment, and one and 24 hours posttreatment were significantly lower than those for Group B (P < 0.05). The primary adverse reactions reported were mild. They included headache, injection site pain, and scalp sensitivity, all of which resolved quickly. LIMITATIONS: The retrospective nature of the study, limited data collection, small sample size, and short follow-up period are notable limitations. Larger-scale prospective studies with extended follow-up periods are recommended for future research. CONCLUSION: local skin precooling is a simple and effective technique for reducing injection site pain during a scalp nerve block. PRP mesotherapy, thereby enhancing patient comfort and compliance. Our study is the first to analyze the analgesic effects of local skin precooling on scalp nerve block injection site pain in patients undergoing scalp mesotherapy.