April 18, 2025, 2:23 pm | Read time: 4 minutes
The neutered cat suddenly goes into heat, or the usually calm dog reacts aggressively? When hormones like estrogen or testosterone are applied externally, such as in gel or cream form, they can sometimes unintentionally enter the pet’s body. The consequences range from behavioral changes to serious health problems.
According to the Federal Office of Consumer Protection and Food Safety (BVL), the use of hormone-containing medications on the skin can lead to unintentional transmission to pets. Hormone creams, in particular, are frequently used and can cause noticeable symptoms of illness in dogs and cats.
When Hormones End Up on Pets
Hormonal preparations applied externally–such as for menopause symptoms–can affect not only the human body. They also pose a risk to pets. Residues of the hormone cream always remain on the skin, which dogs and cats can ingest by licking faces or hands. Even though the concentrations are usually low, the hormones can have an effect. The transmission of hormones can even lead to symptoms of illness in pets, warns the Federal Office of Consumer Protection and Food Safety (BVL).
How Hormones Enter the Pet’s Body
Hormonal residues can be absorbed in two main ways: orally, through licking, or through the skin. Both methods are not uncommon in the daily lives of pet owners. Dogs, in particular, like to lick their humans’ faces and hands while cuddling. Cats also “groom” the skin of their human cuddle partners with their rough tongues. Additionally, dogs and cats might ingest the hormone cream orally if they chew on medication packaging.
Transmission through the skin mainly occurs when petting the animal before washing hands. Close physical contact–such as cuddling or sleeping together in bed–also facilitates the unintended transfer of active ingredients.
A combination of both is also conceivable: for instance, if the cat grooms itself after close contact and ingests hormones distributed in its fur through the mouth, as the BVL adds.
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What Happens When Dogs and Cats Ingest Hormone Cream?
Whether an animal reacts to the ingested hormones depends on the type of hormone, as well as the gender and species of the animal. Contact with a hormone cream containing estrogen or estradiol can cause swelling of the nipples in both male and female dogs and cats. Female dogs may show symptoms of heat–including vulva swelling and bloody discharge. Male dogs may exhibit a drooping foreskin, a reduced penis size, or difficulty defecating, according to the BVL. Female cats, on the other hand, may show signs of persistent heat.
If testosterone preparations enter the animal’s body, they can also trigger noticeable behavioral changes. According to the BVL, typical behavioral abnormalities include aggression toward other animals and humans, as well as increased libido. Additionally, greasy skin problems may occur.
How to Protect Dogs and Cats from Hormonal Preparations
Effective protection for dogs and cats begins with the application of hormone cream: It is important to wash hands thoroughly after application and to avoid contact between the pet and treated skin areas. The affected area should be covered with clothing if possible.
Since many estrogen gels are applied to the arms, caution is advised if the pet is frequently picked up or carried. In such cases, consulting with the treating physician may be advisable. It may be possible to change the application site–for example, to the thighs.
The timing of application also plays a role. The BVL recommends: Those who sleep in bed with their dog or cat should avoid applying hormone creams in the evening. This is because the concentration of active ingredients on the skin is highest immediately after application.
With material from dpa