Alpha hydroxy acid (AHA) and beta hydroxy acid (BHA), most commonly known as glycolic and salicylic acid, are members of the larger family of acids known as chemical exfoliants.

Both AHAs and BHAs contain a carboxylic acid group that allows them to penetrate the surface of the skin, where they then dissociate into their respective acid components and eventually work to break down the "glue" that holds dead cells together on the outermost layer of our skin. This allows for those cells - AKA dry flakes or rough patches - to slough off more readily, revealing smoother, younger-looking skin underneath.

"By exfoliating, AHAs and BHAs help remove the uppermost layer of dead cells from the skin's surface," says New York City dermatologist Dr Dennis Gross. "They also have anti-inflammatory properties that make them ideal for many skin types- people with acne, rosacea, and atopic dermatitis [eczema ] in particular, because these conditions are characterised by redness, flaking skin, and inflammation."

In addition to being a classic ingredient in the fight against acne, salicylic acid is also a top-notch oil-controlling agent. AHA and BHA can be found in a wide range of skincare products, such as creams, serums, toners, masks, and even cleansers. When shopping for an AHA or BHA product, Dr Gross says it's important to look for a product with a concentration of between 0.5% and 4%, although some can go as high as 10%.