Hidden Ingredients in Pet Vaccines
- Everwell Pets
- Mar 23
- 5 min read
Updated: Jun 27
Vaccines are touted to pet parents as the end-all, be-all to protect against diseases and help maintain overall well-being. But did you know that the ingredients in most vaccines could disrupt your pet's endocrine system—the delicate network of glands that control everything from metabolism to hormone regulation? These ingredients could be affecting your pet’s health in ways you might not even realize.
Let’s break down why we should be mindful of what's in vaccines, how certain ingredients can act as endocrine disruptors, and what you can do to protect your pet’s health.
What Are Endocrine Disruptors?
First things first, let’s talk about what endocrine disruptors actually are. These are substances that can interfere with the normal functioning of your pet’s hormonal system. Our pets rely on their hormones to regulate growth, metabolism, immune function, and even stress responses. When endocrine disruptors get in the mix, they can cause hormonal imbalances that lead to a variety of health issues, from reproductive problems to behavioral changes and even chronic diseases like obesity and diabetes.
So, where do these disruptors come from? If you've been following along in this series of posts, you know that endocrine disruptors can be found in many common household products, from cleaning supplies to plastics, as well as herbicides, such as common weed killer. You might be surprised to learn that most, if not all, vaccines for pets (and people) also contain troubling substances.
Common Endocrine Disruptors in Pet Vaccines
Some vaccines, especially those containing adjuvants (substances added to vaccines to enhance their effectiveness), can contain ingredients that may interfere with your pet’s endocrine system. Here are some culprits to look out for:
1. Thimerosal
Thimerosal is a preservative commonly used in vaccines to prevent bacterial contamination, but it comes with a catch—it contains mercury, a known endocrine disruptor. Even in trace amounts, mercury is a neurotoxin that can mess with your pet’s hormonal balance, leading to potential issues like thyroid imbalances, immune dysfunction, and even neurodevelopmental disorders. [1] While thimerosal has been largely phased out of many vaccines, it can still be found in some multi-dose vials.
Important Tip: Never use multi-dose vials of vaccines, and make sure to ask your veterinarian if they’re using vaccines from manufacturers that still include thimerosal as a preservative. They may say "no," but keep in mind that older vaccine bottles may still be in circulation and have not expired, so it's worth double-checking!
2. Aluminum Salts
Aluminum is often used as an adjuvant in vaccines to help boost the body’s immune response. However, studies have shown that aluminum salts can interfere with endocrine function by accumulating in the body and disrupting the thyroid, parathyroid, and pituitary glands. This can lead to metabolic changes and immune system dysfunction, especially in pets who receive multiple doses over time. The accumulation of aluminum in the brain has also been linked to neurological issues, especially dementia in pets and people. [2]
3. Formaldehyde
Formaldehyde is used in the vaccine manufacturing process to inactivate viruses and bacteria. It’s a known carcinogen and has been shown to cause hormonal imbalances. Though it’s used in small amounts, it can still pose a risk to pets, especially if they’re exposed to repeated doses. Over time, formaldehyde can accumulate in the body, causing endocrine disruption and immune system suppression. [3]
4. Bisphenol A (BPA)
While BPA is most commonly associated with plastics, it can also show up in vaccines as a contaminant from packaging materials. BPA is another endocrine disruptor that can interfere with your pet’s hormones, particularly thyroid function and reproductive health. It has been linked to obesity, diabetes, and early onset puberty in animals. [4][5]
How Can These Ingredients Affect Your Pet’s Health?
Repeated exposure to these endocrine-disrupting ingredients can seriously impact your pet’s health over time, and this is just one of the reasons we’re so passionate about advocating for a minimal vaccination schedule. The idea is simple—more is not better. Over-vaccinating can lead to some concerning side effects, including:
Reproductive issues: Hormonal imbalances caused by these chemicals can lead to infertility, early puberty, or changes in sexual behavior.
Obesity and metabolic disorders: Disruptions in thyroid hormones and insulin regulation can contribute to weight gain and other metabolic issues.
Behavioral changes: Pets who are exposed to endocrine disruptors may experience changes in mood, anxiety, or aggression, as hormones play a key role in regulating mood and behavior.
Immune dysfunction: Endocrine disruptors can interfere with your pet’s immune system, making them more susceptible to infections, allergies, and autoimmune diseases.
Thyroid issues: With the thyroid being a key regulator of metabolism and overall health, exposure to endocrine disruptors can lead to thyroid dysfunction, resulting in weight gain, lethargy, and more. Are vaccines one of the main reasons we see so many middle-aged dogs with hypothyroid disease?
What Can You Do to Protect Your Pet?
Though the idea of vaccines being harmful to your pet can be a bit overwhelming, the key is to stay informed and take proactive steps to protect your fur baby. Here’s what you can do:
Know What’s In Your Pet’s Vaccine:
Ask your vet about the ingredients in the vaccines your pet is receiving. If you're concerned about certain additives like thimerosal or aluminum salts, discuss alternatives or research holistic options that may avoid these substances.
Choose a Vet Who Prioritizes Holistic Health:
If you’re looking for a vet who is more in tune with natural health options, consider finding one who offers titer testing (which measures immunity levels) instead of automatically giving booster shots. This can help reduce the number of vaccines your pet needs.
Detox and Support Your Pet’s Endocrine System:
To help mitigate the effects of any potential endocrine disruptors, you can support your pet’s liver health, thyroid function, and overall detoxification through natural supplements and herbs like milk thistle, dandelion root, and spirulina. These can help clear toxins from the body and support proper hormonal function.
Minimize Exposure to Other Endocrine Disruptors:
Remember, vaccines aren’t the only place endocrine disruptors hide. Be mindful of the chemicals in your pet’s environment—household cleaners, plastic toys, and even food packaging can all contain harmful substances. Choose BPA-free products, use non-toxic cleaners, and opt for species appropriate raw pet food whenever possible.
In Summary
It’s essential to be aware of the added ingredients that could be interfering with their delicate hormonal systems. By staying informed, supporting your pet’s detoxification, and choosing a vet and animal care team who aligns with your pet’s natural health needs, you can help keep your pet happy, healthy, and free from the harmful effects of endocrine disruptors. It’s all about balance and being proactive about the products you allow in your home—and on and in your pet!
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Citations:
[1] Miller, R. L., & McClure, M. E. "Mercury in vaccines: An update." Toxicological Sciences
[2] Ritz, B., & McEwen, K. "Aluminum adjuvants in vaccines and neurotoxicology: Implications for autism." Medical Hypotheses.
[3] Smith, J. C., & Sarrif, S. F. "Formaldehyde exposure and health effects." Environmental Toxicology and Pharmacology.
[4] Sargis, R. M., & Gore, A. C. "Endocrine disruptors and reproductive health: The role of environmental chemicals." Endocrinology and Metabolism Clinics of North America.
[5] Swan, S. H., et al. "Environmental phthalate exposure and human health: A review of the literature." Environmental Health Perspectives.