Tuesday, September 20th, 2011

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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12 thoughts on “Will my skin care products go bad if left in the heat?

  1. Ana

    Wow, good to know! I am always a bit paranoid about my products going bad in the summer, even if they are just sitting in my bathroom, because it can get quite hot where I live.

  2. Thank you for this post. It has answered many questions I wanted to ask “someone”. :)

  3. heidi

    this may be true in most places but I’m inclined to disagree where I live, Arizona. In the summer time our high is often above 115 which in and of itself wouldn’t concern me BUT our car can literally turn into an oven at about 160 degrees. Every year children and animals die who are left in the car and I can vouch personally for many a ruined and separated moisturizer. The packaging melts so while 115 might work for most places it doesn’t here.

  4. Joyce

    very interesting. So i was wondering how the contribute to temptalia thing is going cause i haven’t seen a post about it, since you said that it would take longer then expected to proces them all

  5. Chynna

    Thank you so much for this post! I’m in central Texas, where we just set the record for the longest, hottest summer in the US since the government starting keeping records. I’ve been concerned about a few things, especially my sunscreens. This is very useful and relevant information.

  6. What a great post! I’ve always wondered and now I feel much better about my products :)

  7. Renee’s response is very consistent with how chemists across the industry test products. Typically 37C and 45C are used for several months. Some companies do an “acid test” by exposing products to 54C for shorter periods of time. The only additional caution I could give is that your product could experience temperatures above the safe test zone; e.g., if they are left back of a hot truck during shipping.

    You should, however, be more careful with perfumes since they tend to be around for a long time and because many of the notes are more heat sensitive. For best results, store perfumes in the refrigerator to protect from heat.

  8. It’s great to know about the “oven” test but for those of us that live in South Florida, that test is about what the typical outside temperature is for 3 months out of the year with higher humidity. If something is left in the car, at any point between, let’s say June-September, you’re looking at an average of 85% humidity and over 120 degrees. I’ve seen more products separate into 2 and 3 strata more times than I can count.

  9. Futuralon

    Ha thanks for the info–I totally got warm cleanser out of the mailbox today :)

  10. Michelle

    I actually work for a chemical company (we are actually a division of the largest chemical company in the world) that manufactures high end raw materials, as well as finished product for the skincare industry, and I have to say this isn’t 100% true. We manufacture some of the most expensive creams for extremely high end well known brands and not every product we manufacture has undergone this testing. I know for a fact that several of our products are manufactured with storage condition labels that actually indicate that exposure to extreme temperatures can effect product quality and effectiveness of delicate raw materials within that product. While it is possible that your cream may be effective after being in the heat, it is also a possibility that some of the more volatile ingredients within might not survive that heating.

  11. jasmine

    hell must be 100 degrees in celcius :)