Ceramides are a type of lipid molecule that are naturally found in the skin's outermost layer, known as the stratum corneum. They play a crucial role in maintaining the skin's barrier function and preventing moisture loss. While ceramides are generally safe and well-tolerated, there are a few ingredients that should be avoided when using products containing ceramides. Here are some substances you should not mix with ceramides:

1. Strong Acids: Avoid combining ceramides with strong acids such as glycolic acid, salicylic acid, or lactic acid. These acids are often used in exfoliating products and can disrupt the skin's pH balance, potentially compromising the effectiveness of ceramides.

2. Benzoyl Peroxide: Benzoyl peroxide is commonly used to treat acne. However, it can be quite drying and irritating to the skin. Combining it with ceramides may lead to excessive dryness and potential skin barrier damage.

3. Retinoids: Retinoids, including retinol and prescription-strength retinoids like tretinoin, are known for their anti-aging benefits. However, they can also cause dryness and irritation. When used in combination with ceramides, the risk of dryness and irritation may be amplified.

4. Harsh Cleansers: Avoid using harsh cleansers that strip the skin of its natural oils when using ceramide-containing products. Opt for gentle, non-stripping cleansers to maintain the skin's moisture balance and support the benefits of ceramides.

It's worth noting that these recommendations are not absolute and may vary depending on individual skin types and sensitivities. If you have any concerns or specific questions, it is always advisable to consult with a dermatologist or skincare professional for personalized advice.