The modification of polyester yarn was carried out with the aim of producing sustainable coatings from from erythritol, gelatine and collagen with the addition of propolis and alginate fibres and a natural plasticiser (glycerine). The advantage of the sustainable coatings is that they consist of compounds that can be taken orally and are therefore suitable for external use. The morphology of the yarn was determined before and after modification with Dino-Lite. The pH value, thickness and linear density were also monitored before and after modification. The results showed that the modification had no significant effect on the thickness or linear density of the yarns. Furthermore, based on the pH results, the modified samples are suitable for external application on the skin. The results of the tensile strength properties of the modified samples showed a decrease in the strength value of the tested samples (the untreated sample has the highest value and the sample treated with erythritol and propolis has the lowest). When analysing the elongation values of the tested samples, it is noticeable that the sample treated with erythritol and propolis has the lowest ability after modification, while the untreated sample also has the highest elongation ability. The modified samples had a very pleasant hand value. The modification of polyester yarn was carried out with the aim of obtaining a future flat textile product that can be used as a medical dressing for chronic wounds.