Many users put their creams in the kitchen fridge – but does that really make sense? We spoke with Cologne specialist Dr. Andreas Kruppa about germ dangers in open jars, the optimal temperature for Vitamin C and Retinol, and the physiological effect of cooled care on the skin.

Design Furniture with Cooling: A Good Idea?

biszet: Dr. Kruppa, we have developed an exclusive design piece of furniture specifically for the bathroom. It is very elegant and contains a special feature that has not existed in this form before. Cosmetics can be stored stylishly and cooled at the same time. What do you think of this idea?

Dr. A. Kruppa: I think the idea is very good. Many women already keep their cosmetics in the kitchen fridge. That is very practical when you don't have to run from the bathroom to the kitchen and back.

Why is Cooled Storage Important?

biszet: Many cosmetics and skin care products bear the label 'please store in a cool place'. Why is cooled storage so important?

Dr. A. Kruppa: After opening the jars, germs such as bacteria and fungi often get into the care products. These are in the air, but are increasingly introduced through use with fingers. This germ colonization can expand much faster at high temperatures than at cooler ones. This is comparable to milk that you forgot to put in the fridge. The germs can develop faster and the milk goes bad.

Cooled Creams in Practice

biszet: Do you also use cooled creams in your daily practice?

Dr. A. Kruppa: Yes, for example after laser therapy, cooled creams with herbal ingredients are applied. These have a pleasantly soothing effect and are decongestant due to the coolness.

The Optimal Temperature Range

biszet: Which temperature range is optimal for storing cosmetics?

Dr. A. Kruppa: Bacteria simply do not feel as comfortable in the cold as in the warmth. They prefer the warm and humid climate that arises especially with solar radiation when condensation settles in the jars. But even at 20 °C, germs multiply significantly faster than at 10 °C. But it shouldn't be too cold either, otherwise the content crystallizes. Therefore, one should better take cosmetics into carry-on luggage on flights, as they are often exposed to temperatures of up to minus 40 °C in the luggage compartment.
I therefore generally recommend storage at approx. 10 °C, collagen-containing products should rather be stored at approx. 12 °C. Vitamin-containing products, on the other hand, prefer storage at 5 to 8 °C.

Influence on Effectiveness

biszet: What influence does cooled storage have on the effectiveness of cosmetics?

Dr. A. Kruppa: Well, first of all, the use of cooled creams and lotions is significantly more pleasant than using uncooled products. Subjectively, a tightening sensation is triggered. This is because the blood vessels initially contract due to the coolness and blood circulation is increased. Then the vessels dilate again and the active ingredients can be absorbed much faster and better.

Heat-Sensitive Ingredients

biszet: Some cosmetics manufacturers even recommend in their leaflets that the 'cream should not be warmed in the hands so that full effectiveness is maintained'. Which ingredients react so sensitively?

Dr. A. Kruppa: That can be completely different ingredients. Many anti-wrinkle creams contain Vitamin C, for example. This oxidizes very quickly and thus loses its effect. Like many other chemical reactions, this process is accelerated by heat supply.
(How fast these chemical processes occur is detailed by Pharmacist Dr. Stockebrand here).

Products without Preservatives

biszet: Many men and women already use care products without preservatives. What are the advantages and disadvantages of such products?

Dr. A. Kruppa: Many patients develop so-called contact allergies to preservatives such as parabens. Eczema develops on the skin, which can be very unpleasant for those affected. Creams without preservatives can spoil faster, however, as germ colonization can occur more easily.

Dangers of Spoiled Cosmetics

biszet: What can a spoiled cream cause on the skin?

Dr. A. Kruppa: In addition to the lack of effectiveness, different skin irritations such as redness, burning and dandruff can occur. You recognize spoiled creams by the fact that they change their smell (they stink), but also their consistency. Often the content separates into thick and thin. These are signs that unwanted chemical reactions have taken place here, which can have a completely different effect on the skin than originally desired.

biszet: Dr. Kruppa, thank you very much for the friendly and informative interview.

Dr. A. Kruppa: You are welcome.

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