Which of the following are methods of epidermal cooling?

The selection highlights several techniques employed to ensure the skin remains cool during procedures like electrolysis or laser treatments. Chilled gel is commonly used because it can provide a soothing layer on the skin, reducing discomfort and protecting against potential heat damage. Contact cooling is another effective method where a device directly applies a cold surface to the skin, helping to dissipate heat generated during the procedure. Cryogen spray is a rapid cooling method that delivers a cryogenic substance onto the skin, offering immediate cooling to reduce pain and inflammation. Lastly, air cooling involves the use of a stream of cool air directed at the treatment area, further helping to maintain a comfortable temperature.

The other options incorporate methods like ice packs and warm compresses that do not effectively correspond to standard practices for cooling during dermatological procedures. Liquid nitrogen, while used for other applications like cryotherapy, is not a typical cooling method for epidermal cooling in electrology. By emphasizing techniques that are widely recognized and validated for their efficacy in cooling the epidermis during treatment, choice B captures the most appropriate and effective methods.