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This post was written by Renée Rouleau, who is a skin-care expert and celebrity esthetician who has been helping men, women and teens attain healthy, glowing, beautiful skin for more than twenty years.

Her philosophy is simple: With the proper tools, effective products and a disciplined approach, anyone can have great skin.  Her skincare line embodies this same approach and follows her dos and don’ts.  In relation to this post, I fully recommend her AHA/BHA Cleansing Gel!

She provides regular skincare advice and tips on her blog, too!

Will my skin care products go bad if left in the heat?

During the summer months, when temperatures are anywhere from 85 to 100 degrees depending on where you live, you might accidentally leave your skin care products in a hot car and wonder if the heat will affect the safety and performance of the product or worse, ruin them. Or, if you order your skin care products online, you will open up your mailbox or see them sitting outside on your doorstep and discover that because of the hot temperatures where you live, your products will be warm to the touch. Because of the heat, you may notice that a gel cleanser, a cleansing lotion, or a moisturizer will have a thinner consistency than normal. These scenarios may leave you wondering if the heat has affected your skin care products. The answer is no.

Heat should not affect the performance of your skin care products. The reason for this has to do with when products are made. When a new product is made in the laboratory, chemists will put it through the “oven test.” This is where a product is put into an oven with temperatures around 115 degrees Fahrenheit with 70 percent relative humidity, and is kept in there anywhere from six weeks to three months. The purpose of the oven test is to determine if a product can stay stable and maintain its integrity, since products can be left in hot cars or in other less-than desirable conditions. Heat can also mimic the long term shelf life of a product to determine if the product will remain constant for a two-year shelf life, and if the ingredients will separate or change consistency. All of the Renée Rouleau products go through this oven test, exposing them to heat over long periods of time to ensure their safety, performance and longevity, so certainly a hot car for a day or two or a hot mailbox for a few hours should not affect the product at all.

Note: The oven test does not factor in UV light, so if your product sits out for long periods of time in UV light or sunlight, this most likely will weaken the performance of ingredients such as antioxidants (which tend to break down in sunlight). So definitely keep your products in a closed cosmetic bag and try not to subject them to long periods in the sun.

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