About 2 1/2 years ago I wrote a post on the challenges of removing microchips in pets (you can find it here). There have been many comments and some good discussions over the years in that post, though I realize that most of my readers would never go back to an old post just to look at the comments. Many people have the mistaken impression that microchips are likely to cause cancer or serious health problems in pets, and have brought these points up on that post. One of the readers recently made the following comment:
With all due respect Dr. Bern, There are many seemingly innocuous things given to animals and people that can cause injury to those who have no tolerance for it. I knew my cat and I know the chip was causing him problems. I am a vaccine injured adult; but many argue that they are harmless. I also had a severe inflammatory reaction to metal clips placed in my breasts after a biopsy to mark the spot. I know I can't tolerate foreign anything in my body; so why not an animal? They are even more sensitive than most people. I would NEVER inflict that chip into another pet again. My hope is that through these discussions, you'll be aware that it could cause an issue for some animal in your practice. Don't overlook the possibility just because you love the product so much.
They brought up a fairly reasonable point, and one worthy of a thoughtful reply. I also thought it would be a good topic to bring up as a separate post. What I have below is an expansion on what I replied on the older blog entry.....
You may not realize it, but there is not a single product, drug, or procedure I do that doesn't carry the potential for some risk. There isn't a single medication or supplement in humans or animal, even over-the-counter ones, that doesn't carry some risk. With every single patient on every single day I have to weigh the pros and cons of every treatment, surgery, and drug that I decide to use. I have to calculate the risk in an individual patient versus the potential benefits. So I am very, VERY aware that ANYTHING I do on a daily basis "could cause an issue for some animal in [my] practice." NOTHING I do, use, or prescribe is completely without risk, no matter how safe it may be for the majority of patients. We as doctors are trained to watch out for these things and sometimes have to decide to withhold a treatment because it is more dangerous than the disease.
What you may be getting confused on is what we call "idiosyncratic" reactions. These are problems that happen without being expected and without the ability to predict it. Believe it or not, we can't tell whether or not a patient will have an adverse reaction until it happens. I may vaccinate 10,000 pets without any problems at all, and then the next one will have a severe reaction. There is no way that I can tell just by looking at a patient whether or not it will have a reaction. And I can't put a patient at risk for disease by assuming that EVERY patient is that 1 in 10,000 case. Most of the time if there is a reaction it is an unpredictable one, even if it is in the list of potential side-effects. Because we don't know which ones will and won't react poorly, we play the odds and handle such problems as they come up.
You were injured by vaccines, and I'm very sorry for that. Does this mean that we should stop vaccine programs across the world that have helped millions upon millions of people and have eradicated some diseases? Because you had a reaction to a vaccine does that mean I shouldn't give them to my children? No, of course not. We know that virtually all people will be fine after receiving vaccines, and unfortunately there is no way for us to pick out the people who will react adversely beforehand. So we take the chance, play the odds (which are stacked significantly in our favor), and handle the rare bad situation when it comes up. No medical profession would in good conscience say that vaccines are always "harmless". But the good ones know that the benefits far outweigh the risks, and the vast majority of the patients will indeed suffer no significant harm. If someone does have a bad reaction we have to handle that and then flag that individual as someone with whom to be cautious with future treatments of a similar kind.
Can microchips cause problems? Sure. But so can anything else we to or give pets. Will most or even a large minority of pets suffer because of microchips? Absolutely, unequivocally NOT! Millions of animals of various species have received microchips over the last 20 years, and less than a fraction of a percent have had any problems at all. I've known many pets who have been reunited with their owners because they lost their collar but had a microchip. Do you think those owners thought the microchip was worth it? Do we continue to use a product that we know is safe in 99+% of patients? Or do we deny them the possibility of safely returning because of a risk of less than 1%.
If you had a 99% chance of winning the lottery would you spend $50 on a ticket?
I will disagree with the statement "they are even more sensitive than most people". This is far from the truth and is a poor statement. Yes, there are SOME things that they are more sensitive to, such as cats with drugs like aspirin or Tylenol, dogs to a component of chocolate, and so on. But there are plenty of things that they are only as sensitive to as humans, or even less sensitive. The above quote is a very inaccurate and misleading blanket statement.
Also, I disagree that foreign objects in the body are highly likely to cause problems. The above reader had complications related to metal clips in her body. However, the majority of other women haven't had any problems (this goes back to the idiosyncratic reaction). Many vets use "hemoclips", which are small, staple-like clamps that can quickly close off blood vessels during a surgery. Those clips stay in the body for the rest of the pet's life, and I've never seen one come back with a problem related to them that required them to be removed.
Now you might say "well, these things are all sterile and designed to be in the body", and you'd be right. So are microchips when implanted properly. But even without sterility, bodies can be tolerant to small objects under the skin. You might be surprised how many times I and other veterinarians have taken x-rays on dogs and cats to discover pellets, BBs, or buckshot. Most of the time the owner was never even aware that the animal had been shot! I have discovered such subcutaneous metal objects literally dozens of times in my career, and virtually every time it was an incidental finding that wasn't causing any problems at all. In fact, unless there is an obvious abscess or swelling we don't go in and surgically remove them. We just leave them where they are and monitor the pet. Believe me, those things from a gun are far more traumatic, irritating, and have a higher potential for infection or other than any microchip. Yet they don't cause problems in the vast majority of patients.
I will disagree with the statement "they are even more sensitive than most people". This is far from the truth and is a poor statement. Yes, there are SOME things that they are more sensitive to, such as cats with drugs like aspirin or Tylenol, dogs to a component of chocolate, and so on. But there are plenty of things that they are only as sensitive to as humans, or even less sensitive. The above quote is a very inaccurate and misleading blanket statement.
Also, I disagree that foreign objects in the body are highly likely to cause problems. The above reader had complications related to metal clips in her body. However, the majority of other women haven't had any problems (this goes back to the idiosyncratic reaction). Many vets use "hemoclips", which are small, staple-like clamps that can quickly close off blood vessels during a surgery. Those clips stay in the body for the rest of the pet's life, and I've never seen one come back with a problem related to them that required them to be removed.
Now you might say "well, these things are all sterile and designed to be in the body", and you'd be right. So are microchips when implanted properly. But even without sterility, bodies can be tolerant to small objects under the skin. You might be surprised how many times I and other veterinarians have taken x-rays on dogs and cats to discover pellets, BBs, or buckshot. Most of the time the owner was never even aware that the animal had been shot! I have discovered such subcutaneous metal objects literally dozens of times in my career, and virtually every time it was an incidental finding that wasn't causing any problems at all. In fact, unless there is an obvious abscess or swelling we don't go in and surgically remove them. We just leave them where they are and monitor the pet. Believe me, those things from a gun are far more traumatic, irritating, and have a higher potential for infection or other than any microchip. Yet they don't cause problems in the vast majority of patients.
So to summarize, I am not ignoring the possibility of problems, and I'm more aware than you may realize that EVERYTHING I do in my profession has potential side-effects, some of them serious. I'm just saying that we should be realistic and look at the likelihood of whether or not something will happen and weigh that against the potential benefits. If the benefit is big and the odds are significantly tilted towards there being no serious side effects, we'd really be careless if we didn't do it.
