Have you ever opened an old hair product only to find it had turned into a stinky, gooey mess? I sure have! I stumbled upon a bottle of conditioner that I had stashed away because I wanted to use it sparingly, only to find that it had gone bad. I was distraught! I’ve come to learn that while most products have an expiry date on the packaging, these tend to rub off with time making it difficult to determine just how much shelf life each one has. Sometimes, like in my case, the odor of a product might signal that a product has expired, but here are four other ways by which to determine the usability of your hair product: 

1. It says so on the packaging

I know I’m guilty of not reading the expiry dates on my hair products. I’m keen to check the dates on products I consume, but for some reason I always assume that products I apply to my hair are within their use by date. This is not always the case. If you have never looked for an expiration date on a hair product, click here to see the symbol you should be looking for. Some products, particularly those that are made of an organic or all-natural base, might have a short shelf life. It’s always worth the time to check when your product will go off by looking at the time stamps on the packaging.

2. Your product is lumpy

Imagine curdled milk and now look at your hair product. If it bears semblance to the former, it’s most likely time to discard it. Oftentimes, products can get denatured when stored at the wrong temperature or if kept on our shelves for too long. If your product used to glide smoothly onto your palms and now it spurts out in unsightly lumps, just dump it.

3. Your product doesn’t perform as it once did

You might find that you’ve been following the exact process as you always have when it comes to your twist out, but somehow now your hair feels crackly, dry or has a gray mask on it. Your product might be to blame for the hair frustration. Every time you open a product (especially if you are dipping your fingers into it) you are exposing the product to the bacteria in your bathroom or shower. If you have been using the same old deep treatment for three years, chances are it is contaminated or it has simply reached its expiration.

4. Your product suddenly causes irritation

This one can be tricky to detect, because if you have trusted a product for years, you wouldn’t think it could turn its back on you. If you have started to experience a mild burn or itch when using your trusty Holy Grail product, you might need to re-examine it. Irritation might be caused by a change in formulation when the product goes off. You’d better toss your old mousse, head over to a dermatologist for treatment, and then re-stock your stash with products within their use by dates.

Reference: Paula's Choice: When to Toss Out Beauty Products

Have you mistakenly used a hair product that had expired? What telltale signs confirmed that it was time to let it go?

This article was originally published in 2016 and has been updated.