Last updated: May 31, 2016

Dealing with oily hair is annoying enough, but feeling like it's still dirty right after you spent all that time (OK, fine, maybe like 15 minutes) washing? The worst. 

Shampoo is meant to rid your hair of all the dirt and grim that builds up throughout the day, so when your locks stop feeling squeaky clean, your formula of choice is the first thing that comes into question. Is it even working?!  But is it really true that your shampoo can lose its cleansing power? Not exactly, says celebrity hairstylist Kerrie Urban.

“Product buildup is a huge reason why it can feel like your shampoo doesn’t work,” she explains. So, it might feel like your favorite wash has stopped working over time, but really, your hair has a layer of build up on the scalp that is stopping your cleanser from breaking through. Uh, not OK. 

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Along with the typical culprits like hairspray and mousse, if your shampoo contains silicones or waxes, they could potentially be plugging up your hair follicles and adding to the problem. 

Luckily, you don’t have to nix your favorite products to keep your hair feeling clean. Instead, Urban recommends a once-a-week cleansing shampoo like Bumble and Bumble Sunday Shampoo ($25, sephora.com).

“If [you] love your shampoo but some days you feel like you need a little more cleansing power, you can throw this in the mix just to remove that buildup and start over.” But, be sure to steer clear of cleansing shampoos if you have color-treated hair, warns Urban. “If your shampoo is not made for color-treated hair, it can be very stripping and you can literally change your color in one wash.”

RELATED: Seasonal Shampoo? Why Switching Up Products Could End Bad Hair Days

She also recommends adding a cleansing shampoo during the summer months, when your hair is extra oily from the heat as opposed to the winter when your scalp can be dried out. 

But how can you make sure you are using the right shampoo in the first place? Urban advises that naturally curly-haired girls look for a moisturizing shampoo that will keep their ringlets hydrated. For straight hair, you might try a volumizing shampoo that will give your strands body. 

There you have it, the shampoo cleansing myth: busted.

This article originally appeared on InStyle.com/MIMI.