Pets are naturally curious, affectionate, and often glued to their owners, which is why accidental exposure to topical hormone products is easier than you might think.
Evidence suggests that pets may absorb oestrogen or testosterone by coming into contact with areas of human skin where hormone gels and creams have been applied.
Forearms are a frequently recommended application site in prescribing guidelines, which could increase the likelihood of direct contact when we are cuddling or stroking our pets.
These everyday behaviours can lead to unintended hormonal effects in pets, which is a risk that many people are not aware of. The good news is this risk can be easily managed with a few small changes. You should not consider stopping any of your prescribed medication if your pet displays signs of hormone exposure.
What are topical hormone products?
Topical hormone products containing oestrogen and testosterone are human medicines applied to the skin as part of hormone replacement therapy (HRT) and testosterone replacement therapy (TRT).
HRT gels and creams are used to help with menopause symptoms, while TRT products are authorised to replace low testosterone levels; a condition known as hypogonadism. There is also a TRT product authorised for use in women for hypoactive sexual desire dysfunction (HSDD).
What signs of accidental hormone exposure should vets and pet owners look for?
Hormonal changes in pets caused by secondary exposure can vary by the animal’s sex, and symptoms can differ depending on whether the animal absorbs oestrogen or testosterone.
Female pets, whether spayed or not, may show signs similar to being in heat, such as vaginal bleeding and a swollen vulva. In pregnant animals, such exposure can lead to birth defects.
Male pets can develop swollen mammary glands and a change in testicular size.
Pets of any sex may experience hair loss, behavioural changes, increased attention from other pets, and reduced growth rate.
If exposed long-term, less common effects like bone marrow suppression may also occur.
What can you do to reduce risk?
To help minimise secondary exposure to your pet, the VMD recommends the following steps
- keep pets away from areas of skin where human topical hormone products have recently been applied
- wash hands with soap and water after application
- cover the application site with clean clothing (such as a t-shirt) once the product has dried
- consult the Patient Information Leaflet that accompanies the product and/or a doctor if concerned
What is the VMD doing about this?
The VMD continually monitors all reports of suspected adverse events (both adverse reactions and lack of efficacy reports), not only from licensed veterinary medicines, but also from human medicines used in animals and accidental exposure to human medicines.
All cases are evaluated, and we carry out statistical analysis on this data to search for groups of reports (a statistically significant number of reports with the same or similar event) which could indicate a problem with a product.
By sharing findings and raising awareness, the VMD aims to support vets and pet owners in making informed decisions when using the medicine.
How do I report an adverse event?
If you are made aware of an adverse event in an animal after (potential) exposure to a human hormone product administered to a human, please report directly to us, via the VMD’s adverse event reporting service.
The VMD will use reports to check if medicines continue to be safe and work as expected, to protect animal health, public health, and the environment.
You can find out more about how we monitor the safety of animal medicines.
Any human adverse reactions to authorised human medicines should be reported to the Medicines and Healthcare Products Regulatory Agency (MHRA) via the Yellow Card scheme.
The MHRA has also published information on the risks to children following accidental exposure to topical testosterone Topical testosterone (Testogel) risk of harm to children following accidental exposure – GOV.UK.
Notes to editors
- This article is the first in a series where the VMD aims to highlight adverse events that are often underreported.
- All pet owners and vets are encouraged to report incidences of accidental exposure to human medicines in animals via our new and improved digital reporting service.
