In a routine you'll most often find them in toners and serums. Use them after cleansing and before your moisturizers, so they prep your skin for the rest of your routine.
They work best for oily and combination skin, especially skin that's prone to acne and breakouts. Normal skin with the occasional blemish benefits too, while dry and sensitive skin should ease in more carefully.
BHAs help with enlarged pores, breakouts, and excess oil. With regular use your skin looks clearer, pores less visible, and texture more even.
They pair well with hydrating ingredients like hyaluronic acid, ceramides, and panthenol, plus niacinamide, which further helps balance oil. Avoid pairing them with other strong acids (AHA) or retinoids in the same routine, since that can leave skin irritated.
Most people use BHAs 2 to 4 times a week, depending on the strength and how well your skin tolerates them. Evenings are best. During the day sun protection is a must, since they can make skin more sensitive.