April 22, 2025, 11:53 am | Read time: 3 minutes
The neutered cat suddenly goes into heat, or the usually calm dog becomes aggressive? When hormones like estrogen or testosterone are applied externally, such as in a gel or cream, they can sometimes inadvertently enter the pet’s body. The consequences range from behavioral changes to serious health issues.
According to the Federal Office of Consumer Protection and Food Safety (BVL), the use of hormone-containing medications on the skin can lead to unintended transmission to pets. Hormone ointment, in particular, are frequently used and can cause noticeable symptoms in dogs and cats.
When Hormone Ointment End Up on Cats and Dogs
Hormonal treatments applied externally—such as for menopause symptoms—can affect more than just the human body. They also pose a risk to pets. Residues of hormone creams remain on the skin, which dogs and cats can ingest by licking faces or hands. Even in small concentrations, these hormones can have an effect. The BVL warns that hormone transmission can lead to symptoms in pets.
How Hormones Enter a Pet’s Body
Hormonal residues can be absorbed in two main ways: orally, through licking, or through the skin. Both methods are common in pet owners’ daily lives. Dogs, in particular, enjoy licking their humans’ faces and hands during cuddling. Cats also “groom” their human companions with their rough tongues. Additionally, dogs and cats might ingest hormone creams orally if they chew on medication packaging.
Transmission through the skin mainly occurs when petting an animal before washing hands. Close physical contact—such as cuddling or sleeping together—also facilitates the unintended transfer of active ingredients.
A combination of both methods is also possible: for instance, if a cat grooms itself after close contact and ingests hormones distributed in its fur, as the BVL notes.
What Happens When Dogs and Cats Ingest Hormone Creams?
Whether an animal reacts to ingested hormones depends on the type of hormone, as well as the animal’s gender and species. Contact with a hormone cream containing estrogen or estradiol can cause nipple swelling in both male and female dogs and cats. Female dogs may exhibit symptoms of heat, including vulva swelling and bloody discharge. Male dogs may show signs such as a drooping prepuce, a reduced penis size, or difficulty defecating. Female cats may display signs of persistent estrus.
If testosterone preparations enter an animal’s body, they can also trigger noticeable behavioral changes. According to the BVL, typical behavioral issues include aggression toward other animals and humans, as well as increased libido. Greasy skin problems may also occur.
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How to Protect Dogs and Cats from Hormonal Treatments
Effective protection for dogs and cats begins with the application of hormone creams: It is important to wash hands thoroughly after application and to avoid contact between pets and treated skin areas. The affected area should be covered with clothing whenever possible.
Since many estrogen gels are applied to the arms, caution is advised when frequently lifting or carrying pets. In such cases, consulting with a doctor may be beneficial. It may be possible to change the application site, such as to the thighs.
The timing of application also plays a role. The BVL recommends that those who sleep with their pets should avoid applying hormone creams in the evening, as the concentration of active ingredients on the skin is highest immediately after application.
With material from dpa