When it comes to incorporating skincare products into your routine, the general rule of thumb is to apply products in order of their consistency, from thinnest to thickest. In this case, lactic acid is typically a thinner, water-based product, while snail mucin is a thicker, gel-like consistency.

Therefore, it is recommended to apply lactic acid first, followed by snail mucin. Lactic acid is an alpha hydroxy acid (AHA) that helps exfoliate the skin, improve texture, and promote cell turnover. By applying it first, you allow it to penetrate the skin and do its job effectively.

After the lactic acid has been absorbed, you can then apply your snail mucin. Snail mucin is known for its hydrating and soothing properties, and it can help with skin regeneration and reducing inflammation. Applying it after the lactic acid will help lock in moisture and provide additional nourishment to the skin.

Remember to always patch test new products and listen to your skin's needs. If you experience any irritation or discomfort, it's best to discontinue use and consult with a dermatologist or skincare professional.