Some ingredients in shampoos can actually irritate the scalp and worsen dandruff. The most common offenders are sodium laureth sulfate (SLS), sodium lauryl sulfate (SLES) and ammonium laureth Sulfate (ALS). Most of these cleansing agents are found in cheap products that you buy at drugstores or grocery stores, but some luxury brands contain them as well. Although these chemicals may help your hair look smooth, they also kill sebum-making bacteria on top of your scalp, which can lead to unhealthy inflammation known as seborrheic dermatitis. This is why it’s important to check ingredient lists carefully before buying a new shampoo or conditioner. If you find an ingredient list with harsh chemicals like this one, don’t be afraid to walk away from the product—you’ll thank yourself for getting rid of it later!