Safety
Overall, collagen and elastin provide pretty much no safety hazards, with few right-to-know acknowledgements (almost none), no demarcations as dangerous goods, and all zeroes on their NFPA ratings. They are stable in average storage conditions and only react when combined with strong oxidizing agents. Some might be concerned as to the cleanliness and ethics of obtaining natural products derived from pig, cattle, rat, and human skin, tendons, and other parts, but they are otherwise safe and healthy to use.
Comparison of several Safety Data Sheets for collagen (including two manufacturers and bovine achilles tendon) show that the only thing to be cautious of when handling the materials is not to breathe in the compound - collagen is typically found in liquid or powder form, and dust can irritate lungs. Further, collagen does decompose and the products can be irritating to the lungs, but the products are unknown. However, there are really no concerns: collagen is rated a 0 for health, instability, and flammability, with no special warnings. It shouldn’t be put with strong oxidizing agents, but really - collagen is truly nontoxic and non-hazardous. This makes sense, as collagen is already found in huge quantities in our bodies; it wouldn’t make sense for it to be toxic.
Similarly, comparison of various elastin safety data sheets show that elastin is somewhat innocuous. Elastin decomposes with fire into unknown products and reacts with strong oxidizing agents, but is otherwise non-hazardous, non-toxic, and perfectly safe for most uses. Most SDS just say to practice good hygiene. Again, like collagen, elastin’s ubiquity in our body’s predicts the findings - that it would be nontoxic and nonhazardous.
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See SDS sources:
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Collagen (Sigma Aldrich): Elastin (Sigma Aldrich):