Food ingredients in cosmetics: If you are not allergic to food, you are allergic to it when you apply it

The core reason for this seemingly contradictory situation is that The immune response mechanisms of the digestive tract and skin are completely different , coupled with the differences in raw material standards, extraction processes, and usage concentrations of the food itself in the two fields of food and cosmetics, there is no logic that "edible ingredients must be safe when applied to the face."

I received a reader inquiry a while ago. The little girl loves to drink avocado milkshake. She has never been allergic to it after drinking it for five or six years. Recently, she followed the trend and bought a facial mask that claims to be "90% freshly squeezed avocado liquid." Half an hour after applying it, her face turned as red as a ripe peach, and she broke out in a dense rash. She went to the hospital to check for allergens. The food IgE test for avocado was completely negative, but the skin patch test was strongly positive for avocado extract. She was still confused when she took the report and said, "I just drank three cups of avocado milkshakes yesterday. How come it doesn't work if I apply it on my face?" ”

In fact, it’s really easy to understand. Just think of the body’s two lines of defense as two completely different security inspection systems: the food you eat has to go through the digestive tract security inspection, where saliva, gastric acid, and various digestive enzymes take turns. Large molecules of allergenic proteins have long been broken down into small molecules of amino acids and peptides. When they enter the blood, they have basically no immunogenicity. As long as you are not a severe food allergy patient, it will basically not trigger an immune alarm. However, the security logic of the skin is to "reject enemies from the outside". Under normal circumstances, even water molecules cannot penetrate easily. If you directly apply an extract containing complete food proteins to your face, and then you have just finished exfoliation, acid brushing, or the redness barrier has been broken during the season, these proteins will directly penetrate into the dermis, and the immune system will treat it as a foreign invader and beat it to death?

What’s interesting is that many people don’t realize that the “food ingredients” added to cosmetics are completely different from the food you usually eat. Don't listen to the nonsense of "edible-grade formulas" by merchants. The Food and Drug Administration has long issued an announcement that there is no such thing as "edible cosmetics". The raw material standards and testing requirements for food and cosmetics are completely two systems. Take honey, which everyone thinks is mild, for example. Edible honey is allowed to contain a small amount of pollen impurities and active enzymes. If it is added directly to skin care products, it will become moldy and deteriorate in half a month without adding a sufficient amount of preservatives. Even if no preservatives are really added, the solvents used in the extraction process and the additives added to stabilize the ingredients may be hidden allergens, which are not the same thing as the pure honey you soak in water and drink.

Of course, there are different voices in this industry. I know several friends who are engaged in research and development of natural and organic skin care products. They feel that the current cold extraction purification technology can reduce the impurities in food extracts to extremely low levels, and the allergenicity rate is even lower than that of many chemically synthesized ingredients. This is not unreasonable, but even the most purified food extracts cannot escape the "concentration" factor - if you eat half an avocado at a time, it will only be a few dozen grams. The concentration of the relevant ingredients dispersed throughout the body after digestion is so low that it can be ignored. However, the local concentration of avocado extracts in skin care products may be dozens of times higher than the amount of skin contact you eat. The immune system has never seen such high concentrations of similar ingredients, and it is normal to trigger an overreaction.

To be honest, half of the cases of allergy I have seen were caused by buying conceptual products from unscrupulous merchants, and the other half were DIYed at home. What about slicing cucumber and applying it on your face, rubbing your face with lemon, or making a mask with yogurt and honey? I always feel like “you can eat it, but what will happen if you apply it on your face”? Last time, a girl applied fresh lemon slices on her own. After applying it, she went shopping for an afternoon. When she came back, her face was two degrees darker and she had blisters. It was the furanocoumarins in the lemon that were responsible. The furanocoumarins she ate were metabolized and there was basically nothing left. If you apply it directly on your face and then expose it to the sun, the photosensitivity reaction will teach you how to behave in minutes.

There is no need to kill all skin care products containing food ingredients just because of this. After all, classic ingredients such as oat extract and madecassoside that have been used for decades do have very good repairing effects. But really don’t hold onto the superstition that “if you can eat it, it’s safe”, especially those with sensitive skin. Before using this kind of product for the first time, you must squeeze a little and apply it behind your ears. Wait for 48 hours without any redness and itchiness before applying it on your face. It is more reliable than hearing a hundred claims from the merchants that it is “purely natural and edible”.

After all, the mouth and the skin are two completely independent systems. Each has its own preferences. Your skin may not like what you like to eat. If you meet someone next time and say to you, "The ingredients in our products are all edible and absolutely safe," will you let them take a sip on the bottle of lotion first? (Just kidding, you will most likely get diarrhea if you drink it).