Collagens I (α1 and α2) and collagen III are the dominant structural molecules in skin, and their higher order structures give it both strength and flexibility. Two amino acids, hydroxylysine and hydroxyproline are unique to all collagens and are intimately involved in fibre formation. Cross-linking, a vital step in collagen fibrillogenesis, contributes greatly to the structural integrity of collagenous tissues with defects in cross-link formation leading to pathogenesis. Because these cross-links form between hydroxylysine residues and/or lysine and histidine residues, we wondered if differences in the pattern of collagen I-hydroxylysine glycosylation would affect the number, location and types of crosslinks formed, and as a result differences in the physiochemical properties of collagen structures. While there are many reports in the literature on the structure and properties of collagen, much of this research was reported last century using less sensitive techniques than those available today (Neuman, 1950). Using different extraction and purification methods to prevent the loss of specific features of the collagen molecule, we showed, using LCMS, that two cross-links recently proposed to be artefacts of extraction (Eyre, 2019), were in fact present in all skins analysed. Mass spectral analysis also revealed that there are interesting differences in the hydroxylysine glycosylation patterns of the collagen α1(I) and collagen α2(I) chains in all skins tested. Furthermore, there were differences in the hydroxylysine glycosylation patterns of the collagens purified from the skins of different animals, and the ratios of the different types of collagen which are extracted from each animal. In addition, amino acid analysis combined with mass spectral analysis showed that on average 70% of proline residues were hydroxylated in collagen I, a figure much higher than previously thought. While these findings need to be confirmed, they challenge some long held beliefs about the collagen molecule and provide a firm foundation for future work.