Questions About Ototoxicity

by Neil Bauman, Ph.D.

A man wrote,

I am familiar with your work on ototoxic substances, which I think does a great service by bringing people’s attention to this menace. However, I have found a couple of inconsistencies in things you have written, and I am requesting clarification.

First, I believe that you recommend 50% diluted vinegar as an ear wash. However, I was quite surprised to find on the Internet that acetic acid (which is found in vinegar) is ototoxic. Are you aware of this?

Second, I have seen recommendations where you promote the use of garlic. However, I believe that your book identifies garlic as an ototoxic herb. It is hard to believe that garlic is ototoxic in any meaningful way. What evidence are you aware of that garlic is ototoxic?

Third, it would be nice if substances that produce permanent ototoxic effects were highlighted. I think the number of ‘truly ototoxic’ substances is much smaller than your book would suggest.

Thanks for your email. I’m always glad to help people understand more about ototoxicity and how it may affect them. And I’m always willing to fix things if I’ve written something wrong, so let’s look at your three points.

1. Acetic acid is ototoxic. I’m glad you brought this to my attention. I wasn’t aware of this. Somehow in all my voluminous research into ototoxic drugs over the years, acetic acid never appeared on my ototoxic “radar”. However, since you wrote me, I’ve done a fair bit of research on acetic acid to find out more about its ototoxicity. Here’s what I found.

It appears that acetic acid is only ototoxic when it gets into the middle ear (through a hole in the eardrum). I could not find any evidence that it is ototoxic when taken internally (or else people who eat pickles, salsa, relish and such-like would be hard of hearing from all the acetic acid in the vinegar in these foods), or when it is used is the external ear canal (like I recommend) when the eardrum is intact.

In the laboratory, researchers found that acetic acid kills the outer hair cells when it comes in contact with them—at least in Petri dishes—so there is no doubt that it is ototoxic to some degree. However, I still believe vinegar is perfectly safe to use in your ear canals as long as your eardrums are intact. Otherwise, don’t use it.

Incidentally, I’ve already added acetic acid into the prototype of the next edition of my drug book.

2. Garlic is ototoxic. Garlic is an excellent herb to help keep us in good health, and I use it myself with no ototoxic side effects. At the same time, I do indeed list garlic as an ototoxic herb in my book, “Ototoxic Drugs Exposed“.

I agree with you that in general garlic is not ototoxic to the average person, so where does this information come from?

The PDR for Herbal Medicines lists garlic as causing vertigo in some people, thus I have listed it. For further clarification, the PDR for Herbal Medicines mentions that it can cause vertigo in “therapeutic doses”. Obviously, high doses of concentrated garlic extract taken daily can and do cause vertigo in some people. That is why I have listed it. However, in normal doses, I don’t think garlic is ototoxic, and I have no hesitation at all in using garlic as often as I want.

The key thing to notice here is that you have to look at the ototoxic information and decide whether you fit the “profile” or not. Just because a herbal can be ototoxic under certain conditions doesn’t mean that you should avoid it. You just have to understand what those conditions are and act accordingly.

For example, say you have been taking large doses of garlic and you start experiencing vertigo, all you have to do is reduce the dose you are taking. You don’t have to avoid garlic altogether unless you are extremely sensitive to it. I explain how to apply this to several potentially ototoxic foods in much greater detail in the section at the beginning of Chapter 15 in the 3rd edition of “Ototoxic Drugs Exposed“.

3. Highlighting truly ototoxic substances. The 3rd edition of “Ototoxic Drugs Exposed” contains information on the ototoxicity of 1,060 different drugs, herbals and chemicals. To be sure, not all of them have the same degree of ototoxicity. A few of them are highly ototoxic, some of them are moderately ototoxic and many of them have a low degree of ototoxicity (or more accurately a low degree of risk of ototoxicity).

Since some people have experienced the various ototoxic side effects for each drug listed, that is why they are there. It is my duty to report this information to warn people about any possible ototoxic risks. Then it is up to each person to decide whether they are prepared to accept that risk or not.

In order to help people decide, since most people reading my drug book are not experts on ototoxic drugs, I have chosen to place all the listed drugs in 1 of 5 risk classes. Note that this is my own subjective interpretation of how much risk there might be of having an ototoxic side effect, and how bad the resulting side effect might be if you take that drug.

For example, drugs with a risk class of 4 or 5 are “truly ototoxic” drugs in my opinion. Drugs in class 3 are “iffy”, whereas those with a risk factor of 1, while ototoxic to someone somewhere, either affect people rarely, and/or do not have serious or permanent resulting ototoxic side effects.

As a matter of information, I list a total of 52 drugs in classes 4 and 5; 68 drugs in class 3 and 730 in classes 1 & 2. Thus, you can see that most drugs are not what you would call “truly ototoxic”. However, they can be ototoxic at times, but probably not all that often. This is small comfort if you are one of the unfortunate ones that gets a side effect from one of the class 1 drugs and discovers that the resulting side effect is permanent. So, even though the risk might be low, you would still want to know about it.

If the information is available, I list whether any given side effect is temporary or permanent. Unfortunately, there is little authoritative information available whether side effects will be permanent or not. I just report the best information I can find.

To complicate matters further, side effects for a given drug may be temporary or permanent. One person could take a given drug and find a certain ototoxic side effect temporary, while another person could take the same drug and discover the side effect never goes away. That’s just the way it is. There is currently no way to know this in advance.

This can even happen to the same person. For example, one man began taking a certain drug and reported to me that his ears began ringing. I suggested it might be the drug, so he stopped taking it for a week or so and found his tinnitus went away. Based on this experience, he decided to put up with the tinnitus while taking the drug for the full duration his doctor had prescribed knowing that when he finished the drug, he could give it another week or so and his tinnitus would be gone.

Imagine his shock when he did this—and discovered to his horror that his tinnitus refused to go away. It was now permanent! This too happens. Again, there is no way to tell in advance whether this will happen to you or not.

Since you don’t know in advance whether any ototoxic side effects will occur, how bad they will be if they do occur and whether they are going to be temporary or permanent, I warn people about all known ototoxic side effects whether they are high or low risk. They can then use this information however they wish. Some people may choose to take the risk and others not to. That is fine. They have made their choice based on the best evidence available to them—and that is as it should be.

Don’t let ototoxic drugs inadvertently damage your ears and leave you with hearing loss, tinnitus or balance problems. To learn which drugs are ototoxic, get the 3rd edition of “Ototoxic Drugs Exposed“. This book contains information on the ototoxicity of 877 drugs, 35 herbals and 148 chemicals.