Yes, you can mix collagen and BHA (beta hydroxy acid), but there are a few things to consider. Collagen is a protein that provides structure and elasticity to the skin, while BHA is an exfoliating ingredient that helps to unclog pores and improve skin texture.

When combining these two ingredients, it's important to ensure that the pH levels are compatible. BHA works best at a low pH, around 3-4, while collagen requires a slightly higher pH, around 5-6, to remain stable. Mixing them together may alter the pH levels and could potentially reduce the efficacy of both ingredients.

To avoid any potential issues, it is generally recommended to use BHA products separately from collagen-based products. You can incorporate them into your skincare routine at different times of the day or on alternate days to ensure that both ingredients can work effectively on your skin.

Always remember to patch test any new products or combinations on a small area of your skin before applying them to your entire face to check for any adverse reactions. Additionally, if you have any specific skin concerns or conditions, it's best to consult with a dermatologist or skincare professional for personalized advice.