Powerful ingredients can irritate sensitive skin, says Dr. Asgari. “Always test a small area before you apply a skin serum widely.” And use caution when combining acid-containing serums with other products that also contain acids. For example, your skin may get irritated if you use a serum with vitamin C (which is acidic) and as well as a retinol cream, or if you use a retinol serum along with a prescription retinol cream.

Brands that sell both formats raise the same caution when they explain how a serum differs from a cream. In its guide on the difference between the two, Aroma-Zone advises making sure the actives in a cream and a serum are compatible, because some are very potent and not recommended for simultaneous use, as is the case with retinoids and exfoliating actives. For anyone applying a retinol face serum before a moisturizer, the brand specifically names vitamin C, AHAs, and BHA as ingredients the cream applied on top should not contain, and suggests a soothing formula instead to help prevent the discomfort sometimes associated with retinoids.

When adding a new serum to your skincare routine, it is best to introduce it gradually rather than using several powerful products at once. Pay attention to how your skin responds and avoid combining ingredients that may increase sensitivity. Choosing compatible products and keeping your routine simple can help you enjoy the benefits of active ingredients while reducing the risk of irritation.

A careful approach to skincare can make a significant difference, especially when using concentrated serums. Always consider your skin type and the ingredients in your other products before adding a new treatment.