Why does povidone-iodine produce more foam the more it is wiped?

Generally, the reason why povidone-iodine produces more foam with continued wiping may include the presence of surfactants that generate foam, reactions upon contact with secretions, influence of wiping pressure and technique, excessively high iodine concentration, or the presence of oil and dirt on the area being wiped. Detailed explanations are as follows:

1. Foam generation due to surfactants: Some povidone-iodine products contain surfactants (such as auxiliary components in povidone-iodine). These substances are inherently foaming; when they come into contact with air or experience friction during wiping, continuous foam can form, which is a normal characteristic related to product composition.

2. Reaction upon contact with secretions: If the area being wiped contains secretions such as pus or exudate, the active ingredients in povidone-iodine may react with proteins or bacterial metabolic byproducts in the secretions, resulting in bubble formation. The amount of foam may correlate with the volume of secretions present.

3. Influence of wiping pressure and technique: Excessive pressure or repeated rubbing during wiping can thoroughly mix povidone-iodine with air, increasing bubble formation. Rapid wiping with cotton balls or gauze can also easily trap air through fiber friction, leading to foam production.

4. Excessively high iodine concentration: If the povidone-iodine concentration exceeds standard medical levels or is not properly diluted according to instructions (some concentrated formulations require dilution), the higher concentration of active ingredients may produce dense foam during application and potentially cause skin irritation.

5. Presence of oil or dirt on the surface: When oils, sweat, or dirt remain on the skin surface, mixing with povidone-iodine can disrupt the liquid’s surface tension, causing foam. This effect is particularly noticeable in oily areas such as the face and neck.

Prior to using povidone-iodine, clean the application site to remove surface contaminants; select an appropriate concentration according to product instructions to avoid excessive strength; use moderate pressure and minimize repeated rubbing during application. If foam is accompanied by redness, swelling, or stinging, discontinue use immediately, wash the area thoroughly, and consult a healthcare professional if necessary.