Papain is found naturally in papaya and is often referred to as a “plant-based pepsin” in reference to the digestive enzyme pepsin that is present in the stomach.
“People with sensitive skin as well as small children should avoid the enzyme as much as possible, and observe the ingredients’ declaration for consumer products as regulated.”
Scientists from the Messerli Research Institute of the University of Veterinary Medicine Vienna, the Medical University of Vienna, and the University of Vienna looked at how papain affects the skin of mice and skin cells in the petri dish.
Their study was published in the Journal of Investigative Dermatology.
On the skin, papain results in a loss of the barrier function. “After just a short period of time, papain increased vascular permeability and inflammatory cells infiltrated the skin,” the researchers report.
Around 2 weeks after being exposed to papain, they found antibodies to papain in the mice. These immunoglobulins are the cause of the allergic reaction toward the enzyme.
The permeation of the skin barrier does not appear to be a prerequisite for sensitization toward papain, the study showed. The enzyme remains allergenic even when its enzymatic function has been blocked. In humans and in animals, diseases of the skin such as atopic dermatitis—commonly referred to as eczema—involve an increased permeability of the skin with a heightened risk for bacterial, fungal, or viral colonisation.
“People with sensitive skin as well as small children should avoid the enzyme as much as possible, and observe the ingredients declaration for consumer products as regulated,” the study authors warn.