It is generally not recommended to use numbing sprays on open blisters or wounds on the feet. Numbing sprays contain local anesthetics that are designed for intact skin application. Applying numbing spray for feet to open wounds or blisters can potentially delay the natural healing process and increase the risk of infection. It is important to prioritize proper wound care, such as cleaning the area gently with mild soap and water, applying appropriate dressings, and seeking medical attention if needed. Consult with a healthcare professional, such as a wound care specialist or podiatrist, who can provide guidance on appropriate wound care techniques and recommend suitable pain management options for open blisters or wounds on the feet.