We got some autologous serum eye drops for our dog to help treat a stubborn ulcer, and she has been on them for a few days now, however, when bringing the drops back from my mums house to mine, I accidently left them out of the fridge for about 1.25 hours (they were inside the house, and the weather isn't hot at the moment).

Now, not sure if it was a coincidence, but we could barely get any drops out of it after that, even though we could still see liquid in there; not a massive amount, so maybe there wasn't enough pressure in the bottle to push it out, combined with not enough force from enough liquid to push it through the dropper?

I did manage to one last drop out of it, barely, once I noticed I hadn't put it in the fridge; however the next time I tried to use it, I couldn't get any drops out no matter how hard I squeezed.

I was going to give it one last try after having it back in the fridge for several hours, and when I shook it up, some liquid started coming out of the top of it even when I was holding it upright, so maybe it's going to start working again - still have to test.

However, if it does work, any idea why that would be? The liquid we could see in there all seemed still normal looking, but is there any possibility that leaving it out of the fridge caused some of it to clot, and clog up the hole? Is that a possibility, or wouldn't these drops have the ability to clot?

I did read that "Serum is the liquid that remains after the blood has clotted", so ideally it shouldn't be able to clot, but I do wonder, as the drops do still have a pinky colour to them, that they could potentially still have a small amount of hemoglobin from residual red blood cells in there, or if there were any remaining platelets or clotting factors in the serum, some additional clotting could have occurred when the serum warmed up to room temperature, and perhaps potentially cause a obstruction of the dropper?

I thought of just giving it a go and if it works, great, however, the reason I am asking about clotting, as I was worried, if there were indeed some clots present, that the presence of such could potentially present a safety issue introducing them into the body?

  • 1
    For future reference, questions here are required to show some degree of prior research, an effort at answering the question yourself. We also don't allow questions that ask for medical advice. Despite these shortcomings, I've gone ahead and provided an answer, but in the future please follow these policies.
    – Carey Gregory
    Commented May 18 at 22:27
  • Should this be moved to i.e. Biology.SE or Pets.SE? I‘m not sure how much this relates to MedicalSciences. In principle, you are right and serum per definition should not be able to clot. Serum (unlike plasma) will still contain all non-coagulatory proteins and they might still aggregate at room temperature if given enough time. // Also, now I‘m really interested in the mechanism of action of autologous serum to treat ulcers. Is it the alpha1-antitrypsin?
    – Narusan
    Commented May 21 at 7:10
  • @Narusan I wasn't sure initially if it more suited biology or medical sciences, but the tags available seemed like MS was more appropriate. As for your question, I think a lot of it has to do with the growth factors contained within the serum?
    – Brett
    Commented May 24 at 17:32

1 Answer 1


Whether it can clot or not is beside the point. Those drops are a natural product derived from your dog's blood and are therefore perishable. I think a small vial sitting out at room temperature for over an hour will almost certainly reach room temperature.

According to the Sierra Eye Bank:

Ideally, the drops will only be out of refrigeration for as long as it takes to apply the prescribed amount to your eye(s). If you must take the eye drops with you when you leave home, they should be transported and stored in a cooler with wet ice from your home freezer. Eye drops that have reached room temperature should be discarded. If there is any question about how long a bottle has been left out, discard it and open a new bottle.

We don't offer medical advice on this site, so I'm not going to tell you what to do, but I think the above statement makes it pretty clear. If you have doubts, call your veterinarian.

  • That was my first concern as well, and is why I called the vet to see if they were still ok to use - whilst our vet we seen wasn't there, they asked another vet who said they were ok to use. Food is perishable as well, but that can be left out of the fridge for 1-2 hours depending on temp, but maybe eye drops are different!? I appreciate the answer, but my question was specifically about the ability of the drops to clot, and if so, does introducing any into the body present any safety issues via this method?
    – Brett
    Commented May 19 at 3:11
  • @BrettMarks I would follow the advice of top eye experts.
    – Carey Gregory
    Commented May 19 at 15:19
  • We're due back at the vet shortly, so maybe we will get some more drops done if needed, and this time, try and be far more careful with them.
    – Brett
    Commented May 19 at 15:35

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