There are no official guidelines to assist in answering this question. I will search for relevant research papers instead.
From the Research
Benefits of Skin Toner
- Skin toner can be beneficial in reducing oiliness of the skin, as shown in a study where guava toner significantly reduced oiliness of the forehead and nose compared to a base toner 1.
- The use of a skin care routine that includes a toner can also improve superficial hydration, deep hydration, skin roughness, mean pore area, melanin heterogeneity, and crow's feet wrinkle depth 2.
- Skin care products, including toners, should be formulated to maintain the skin's physiological acidic state, which is crucial for the permeability barrier function, stratum corneum integrity/cohesion, and antimicrobial defense 3.
Importance of Skin Care Routines
- Daily skin care routines are fundamental aspects of clinical nursing practice and can have a substantial impact on the prevention and treatment of skin conditions 4.
- Structured skin care programs that include low-irritating cleansers and application of leave-on products, such as toners, can be beneficial in maintaining skin integrity and preventing skin damage across a wide range of different skin conditions 4.
- The use of antioxidants, which can be found in some skin toners, can improve skin health and youthfulness by protecting the skin from damage caused by free radicals 5.
Key Considerations
- When selecting a skin toner, it is essential to choose a product that is suitable for your skin type and needs, and to follow a consistent skin care routine that includes other products such as cleansers and moisturizers 2, 4.
- Skin toners can be formulated with various ingredients, such as guava extract, that can provide additional benefits for the skin 1.
- The effectiveness of skin toners can depend on various factors, including the individual's skin type, the formulation of the product, and the frequency of use 1, 2.