United States in December 2020, for the treatment of actinic keratosis on the face or scalp. Procedures Cryotherapy Liquid nitrogen (−195.8 °C) is the most commonly used destructive therapy for the treatment of AK in the United States. It is a well-tolerated office procedure that does not require anesthesia. Cryotherapy is particularly indicated for cases where there are fewer than 15 thin, well-demarcated lesions. Caution is encouraged for thicker, more hyperkeratotic lesions, as dysplastic cells may evade treatment. Treatment with both cryotherapy and field treatment can be considered for these more advanced lesions. Cryotherapy is generally performed using an open-spray technique, wherein the AK is sprayed for several seconds. The process can be repeated multiple times in one office visit, as tolerated. Cure rates from 67 to 99 percent have been reported, depending on freeze time and lesion characteristics. Disadvantages include discomfort during and after the procedure; blistering, scarring and redness; hypo- or hyperpigmentation; and destruction of healthy tissue. Photodynamic therapy AKs are one of the most common dermatologic lesions for which photodynamic therapy, including topical methyl aminolevulinate (MAL) or 5-aminolevulinic acid (5-ALA), is indicated. Treatment begins with preparation of the lesion, which includes scraping away scales and crusts using a dermal curette. A thick layer of topical MAL or 5-ALA cream is applied to the lesion and a small area surrounding the lesion, which is then covered with an occlusive dressing and left for a period of time. During this time the photosensitizer accumulates in the target cells within the AK lesion. The dressings are then removed and the lesion is treated with light at a specified wavelength. Multiple treatment regimens using different photosensitizers, incubation times, light sources, and pretreatment regimens have been studied and suggest that longer incubation times lead to higher rates of lesion clearance. Photodynamic therapy is gaining in popularity. It has been found to have a 14% higher likelihood of achieving complete lesion clearance at 3 months compared to cryotherapy, and seems to result in superior cosmetic outcomes when compared to cryotherapy or 5-FU treatment. Photodynamic therapy can be particularly effective in treating areas with multiple AK lesions. Surgical techniques Surgical excision: Excision should be reserved for cases when the AK is a thick, horny papule, or when deeper invasion is suspected and histopathologic diagnosis is necessary. It is a rarely utilized technique for AK treatment. Shave excision and curettage (sometimes followed by electrodesiccation when