Background: pH is known as an important parameter in epidermal barrier function and homeostasis. Aim: The impact of age and body site on skin surface pH (pHSS) of women was evaluated in vivo. Methods: Time domain dual lifetime referencing with luminescent sensor foils was used for pHSS measurements. pHSS was measured on the forehead, the temple, and the volar forearm of adult females (n = 97, 52.87 ± 18.58 years, 20–97 years). Every single measurement contained 2,500 pH values due to the luminescence imaging technique used. Results: pHSS slightly increases with age on all three investigated body sites. There are no significant differences in pHSS between the three investigated body sites. Conclusion: Adult pHSS on the forehead, the temple and the volar forearm increases slightly with age. This knowledge is crucial for adapting medical skin care products.