Pineapple contains the enzyme bromelain, which can break down the connecting layers between skin cells to effectively exfoliate skin. Bromelain, when used on its own, is a more effective source of exfoliation than pineapple and does not have the potential irritating properties of the pineapple fruit. Allergic reactions may occur in individuals who are sensitive or allergic to pineapples and cross-reactivity may occur in those sensitive to latex or rye-grass. 

Bromelain is a mixture of enzymes found in the pineapple plant and is obtained from the stem or fruit of the pineapple. The term “bromelain” may refer to either of two protease enzymes extracted from the plants of the family Bromeliaceae, or it may refer to a combination of those enzymes along with other compounds produced in an extract. It is sold in the form of a powder or liquid tincture and it may be used alone or in combination with other ingredients. While there have been several studies on the use of bromelain for nasal swelling and inflammation, little research has been done on other uses of bromelain. Some research in human and animal studies has found that topical bromelain formulations may help remove dead skin from burns. However, not enough evidence exists to show whether topical bromelain helps to treat burns and other wounds. 

The moisturizing activity of pineapple is due to its carbohydrates and α-hydroxy acids (AHA) content. Carbohydrates are widely used in cosmetics for their ability to maintain skin hydration. Monosaccharides and oligosaccharides are able to hold water and help maintain the moisture level of the stratum corneum (outermost layer of skin). These active compounds act by forming hydrogen bonds, preventing massive water loss and stopping dehydration. Additionally, some of these compounds form a protective film on the skin, preventing and slowing down transepidermal water loss (TEWL).

The exfoliating activity of pineapple is due to α-hydroxy acids (AHA) that acts at the stratum corneum level. AHA’s act on the “glue” between dead skin cells, effectively making the stratum corneum thinner and improving skin flexibility. 

Cosmetic applications for pineapple include moisturizing and emollient products, anti-aging, exfoliating and firming products, as well as hair coloring products. Like other skincare products, proper testing should be performed to determine the likelihood of allergic reaction based upon the usage rates and form of pineapple used in the formulation. Proper labeling and appropriate warning and caution statements should be used. The Food and Drug Administration recommends that the labeling of a cosmetic product containing an AHA as an ingredient and that is also topically applied to the skin or mucous membrane (such as the lips) bear a statement advising that sun protection is recommended after using the product.