What is the protein that reduces water loss at the skin surface?

Keratin.

Explanation:

Keratin protein is present in hair, hooves, nails and skin. keratin is a class of the fibrous structural protein that protects the skin from damage.

Keratin protein reduces the water loss at the skin surface. The keratin is insoluble in water and cannot be dissolved in organic solvents also. Keratin also protect the skin from the stress.

Thus, the answer is keratin.

explanation:

for example, code 28039 - excision, tumor, soft tissue of foot or toe, subcutaneous, 1.5 cm or greater, appears before 28043 - excision, tumor, soft tissue of foot or toe, subcutaneous; less than 1.5 cm.