1. Acidity regulator/buffer-change or maintain the acidity or alkalinity of food/cosmetics.
2. Exfoliating-remove dead cells on the skin surface
3. Preservatives-prevent and inhibit the growth of harmful microorganisms
Malic acid is a dicarboxylic acid produced by all living organisms, giving fruits a pleasant sour taste, and used as a food additive (E number 296). Malic acid is the main acid in many fruits, including apricots, blackberries, blueberries, cherries, grapes, kiwis, peaches, pears, plums, and quinces, and is low in other fruits (such as citrus). It contributes to the sour taste of green (immature) apples. It is found in grapes and most wines, sometimes as high as 5 grams per liter. It imparts a sour taste to the wine, but as the ripeness of the fruit increases, the sourness will decrease. The taste of malic acid is very clear and pure in rhubarb. Rhubarb is a plant and it is the main flavor. It is also an ingredient in some artificial vinegar flavors, such as "salt and vinegar" flavored potato chips.
It is approved as a food additive in the European Union and is generally considered a safe food substance in the United States.
1. CANADA INGREDIENT HOTLIST, a list of ingredients restricted to be used in cosmetics 
2. US FDA Food Additive Status List 
-Malic acid, L-malic acid
3. Food additives approved by the European Union 
4. List of designated food additives specified in Article 10 of the Food Sanitation Law of Japan
-DL-malic acid (dl-malic acid)
5. U.S. FDA Recognized As Safe (GRAS) Food Substances (21 CFR 184) 
-§ 184.1069-Malic acid
Safety and Hazard (UN GHS):
1 . Harmful if swallowed (H302)
2 . Cause skin irritation (H315)
3 . Cause severe eye irritation (H319)
4 . May cause respiratory irritation (H335)
Potential health problems:
1 . Epilepsy (PubMed ID: 20691264)
Potential health benefits:
1 . Overdose (PubMed ID: 15337580)